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Legal
aternal N utri'otion
.IIIReport to the Ministry of Health
from
Patsy WatsonSenior Lecturer in NutritionDepartment of BiochemistryMassey UniversityAlbany CampusPrivate Bag 102-904North Shore MSCA UCKLAND
09897931 October 1996
STACK
wQ175[Q]WAT1996
MOH Library
II IIIIUI IIfl I98979M
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ACKNOWLEDGEMENTS
The statistical advice and assistance with the analysis in this report given by Dr BarryMcDonald, Biometrician has been much appreciated.
In addition the assistance of the following people in data collection, entry, processing andanalysis is gratefully acknowledged:
Mrs Judy Matheson
Mrs Vicki Cameron
Ms Marianne Salmon
Ms Lisa Ward
Mrs Judi Scheffer
Ms Alexandria Meier
Dr Mark von Veh
Ms Janene McNamara
Ms Cara Mackle
Ms Geraldine Wood
Mr Andrew Trow
Finally the skills of Mrs Fleur Daniels in presentation and layout are recognized withthanks.
This study was made possible by grants from the following:
New Zealand Ministry of Health
New Zealand Lottery Science Board
Palmerston North Medical Research Foundation
Massey University Research Fund
SUMMARY1. Two hundred and fourteen women volunteered for the study, ten miscarried and seven
withdrew, leaving 197 for whom data collection was complete. Of these subjects 89.8%were of European origin and 6.6% Maori.
2. The data collection period lasted from the fourth month of pregnancy to 1 year afterbirth. During this period 16 weighed diet records, 6 minute by minute daily activityrecords, 35 skinfold measurements, 5 weight measurements plus social, cultural, medicaland lifestyle details were collected from all subjects.
3. More subjects worked in higher socio-economic group occupations. Twenty-one subjectswere supported by benefits only.
4. Mean energy intake of the sample in month 4 and month 7 of pregnancy was 8.9 MJ/day.Twenty-five percent of subjects had energy intakes> 10.4 MJ/day and 20% had intakes <7.0 MJ/day. There was no significant difference in energy and nutrient intake betweenthe fourth and seventh month of pregnancy. The mean percentage of total energy fromprotein, fat and carbohydrate was close to Nutrition Task Force recommendations.
5. Protein intake was below the recommended level of 0.8 g/kg of body mass in 20% of allsubjects. Animal protein and cholesterol intake was excessively high in some. Fibreintake was low with 40% of subjects consuming less than 20g a day.
6. Intake of most nutrients was adequate, however a substantial percentage of subjects hadcalcium, iron, zinc, selenium and folate intakes less than two-thirds of the Australian RNIfor pregnancy. Vitamin A and Vitamin C intakes were very high and in some casesexcessive.
7. The mean weight of food eaten by women on a benefit or in the lower socio-economicgroups was significantly less than that eaten by higher socio-economic groups. Thisresulted in a significantly lower nutrient intake in the former groups, with calcium, zinc,iron, selenium, and total folate intakes substantially below recommended levels. Thebenefit group had the lowest intake levels. The contribution of fat, carbohydrate andprotein to total energy was not different in the lower socio-economic groups. They justate less. There were some highly significant negative impacts on growth to 1 year ofchildren born to these lower socio-economic group mothers.
S. The anthropometric measurements indicated that the sample ranged from the extremelylean (borderline malnutrition) to the obese. On average 12 months after birth, thewomen were still 2.3 kg heavier than before pregnancy. Only 20% of women returned totheir pre-pregnancy weight.
9. Women generally started putting on weight around the 13th week of gestation. Thosewomen who put on weight before the 13th week lost only 20 to 50% of that weight afterbirth. Activity levels were more important than diet in determining weight loss afterpregnancy. The lower the socio-economic group, and the higher the pre-pregnancy BMI,the biceps to costal ratio, the older the women, and the more pregnancies she had had,the greater the weight gain post pregnancy. Of the significant nutrients high fructoseintakes (high fruit juice and carbonated bevera ge) and high saturated fatty acid intakes(high fatty meat, dairy product, cake and biscuit intake) were the most importantindicators of weight gain.
10. There were many more heavy babies at birth and 1 year (> 97th percentile) than onewould expect when compared with the NCHS growth curves.
11. Highly significant positive influences on birthweight included pre-pregnancy BMI, thenumber of recent pregnancies, and zinc intake. Highly significant negative influencesincluded the biceps to costal skinfold ratio, the length of time spent sleeping and lying,smoking, high wholegrain and high tea intakes (high manganese) and high animal proteinintakes (high S).
12. Highly significant positive influences on growth in terms of weight for height at one yearincluded; the sex of the baby, its birthweight, weight gain to 6 weeks and monounsaturatedfatty acid and Vitamin E intake of the mother during pregnancy. Highly significantnegative influences on growth at one year included the length of breastfeeding andpolyunsaturated fatty acid and cholesterol intake of the mother during pregnancy.Whether these effects of maternal nutrition intake during pregnancy on growth at oneyear are a result of some influence of maternal diet on the foetus itself, or an indicator ofthe type of weaning food fed the infant cannot be determined.
CONTENTS
1. Objectives. 1
2. Introduction . 1
3. Methods ................................. ................................................................................. 23.1Pilot Studies Completed...............................................................................23.2Techniques of Data Collection......................................................................33.3Data Collection Programme........................................................................43.4Ethical Approval..........................................................................................43 .5Subjects ................................................................................. ........................5
4. Cultural and Socio-Economic Background of Subjects...................................64 . 1Results........................................................................................................... 64.2Discussion of Results.....................................................................................8
5. Body Weight and Body Fat Levels of Subjects..................................................95.1Methods of Analysis......................................................................................95.2Results ..........................................................................................................JO5.3Discussion of Results .................................................................................... 11
6. Dietary Intake of Subjects ................................................................................... 166.1Methods of Analysis...................................................................................... 166.2Results..........................................................................................................166.3Discussion of Results ..................................................................................... 23
7. Effect of Socio-Economic Group on Dietary Intake of the Mother,and Anthropometric Measurements of Mother and Baby..............................257.1Methods of Analysis......................................................................................257.2Results..........................................................................................................267.3Discussion of Results....................................................................................26
S.Factors that Influence the Loss of Fat Accumulated During Pregnancy308.1Methods of Analysis ...................................................................................... 308.2Results...........................................................................................................8.3Discussion of Results ....................................................................................39
9. Infant Measurements from Birth to One Year 509.1Methods of Analysis......................................................................................509.2Results..........................................................................................................509.3Discussion of Results....................................................................................54
10. Influences on Babies Birthweight ..................................................................... 5510.1Methods of Analysis......................................................................................5510.2Results ..........................................................................................................5510.3Discussion of Results....................................................................................60
11. Influences on Infant Growth at One Year........................................................7111.1Methods of Analysis......................................................................................7111 .2Results ..........................................................................................................7111.3Discussion of Results .................................................................................. ..76
12. References............................................................................................................ 84
13. Appendix One ........................................................................................................87Distribution of Nutrient Intake at Month 4 and Month 7 of Pregnancy.....................87
1. OBJECTIVES
To analyse data from a completed study of the nutritional status of 197 pregnant womenfrom the fourth month of pregnancy to one year after birth and provide reports to theMinistry of Health on:
(a) Maternal nutrient intake during pregnancy highlighting possible inadequacies.
(b) Maternal nutritional factors which influence birth measurements andmeasurements at one year.
(c) Factors common to these women who after birth, do, and do not lose the fataccumulated during pregnancy.
2. INTRODUCTION
A study of the nutrient intake, energy expenditure and fatness levels of urban and rural 15year olds carried out by the applicant revealed that a disturbing number of girls wereunderweight with inadequate diets'. Similar results were found in a Christchurch study5and a recent Department of Health stud y6. This raised concerns about the next stage inthe life-cycle, motherhood, as a longitudinal Harvard study has shown that dietarypatterns established after the maximum growth spurt in adolescence persist intoadulthood.7
Overseas studies have shown that maternal height, pre-pregnant weight for height, weightgain and energy intake during pregnancy are all independently associated with birthweight8 ". Numerous other non-nutritional factors have also been shown to affect birthweight9" 2 . Birth weight is generally considered to be the best measure of the quality ofpregnancy' 3 . Babies born with birth weights in the 2.5-4.2 kg range seem to have optimalchances of survival in the first year of life8 ' 9 . Over the last 10 years for which figures areavailable in New Zealand, the number of babies born has remained relatively constant,however the number of low birth weight babies (5.8% or —3000) and high birth weightbabies (12.6% or —7000) has slowly increased ' 4 " 5. Two important studies have beenpublished that quantify the contribution social, cultural and geographical variables, parity,education and the ingestion of toxic substances, make to the risk of birth of small forgestational age babies in New Zealand. The first considered all live births between 1981and l983'. The second studied the background to 1800 randomly selected births ' 6 . Theresults of these studies showed that socio-economic status, educational level, Maoriparentage, birth order, smoking and marijuana use, and lack of ante natal care allcontributed to the increased risk of a small for gestational age birth, with smokingappearing to be the most important risk factor. However in New Zealand where obviousmalnutrition is uncommon and diet variability great it would also be useful to quantify theeffect maternal nutritional status has on birth weight. This research is particularlypertinent considering the important relationship Barker and others have found betweenretarded growth in foetal life and infancy, and later incidence of high blood pressure, non-insulin dependent diabetes and mortality from cardiovascular disease 11 , 20 ,
1
3.
Little research has been carried out in New Zealand on the nutritional status of pregnantwomen. A recent study gives some information on the energy and nutrient intake of 115women in the second and third trimesters of pregnancy 21 . No correlation was foundbetween energy intake, weight gain, final weight or infant birth weight. This result wasnot unexpected for dietary intake considering the experimental design. A recentlypublished study on 95 pregnant Dunedin women, reported the results of a 3 day weigheddiet survey, taken at 3 intervals spread tnrough pregnancy 22 . The results indicated that asignificant proportion of women were eating inadequately at that time. Another studyusing as its basis the Hillary Commission Lifestyle Questionnaire collected informationfrom 183 Dunedin women a week after giving birth. Details of smoking habits, alcoholand food consumption, and participation in physical activities before and duringpregnancy were collected retrospectively 23 . More recently alcohol consumption duringpregnancy has been studied24.
However no New Zealand study has sought to quantitatively measure: energy andnutrient intake, 24-hour physical activity and body fat levels in pregnant women, or relatethese variables to infant birth measurements as is proposed in this study. 0METHODS
33 PILOT STUDIES COMPLETED
3.11 Nutrient Intake and Energy Expenditure PilotA 14 day study on 21 women in the 18-35 age group was used todetermine by analysis of variance the sample size and number ofmeasurement days required to accurately assess mean group nutrientintake, and the number of measurement days necessary to provide accurateindividual assessment of energy and nutrient intake and energyexpenditure. Knowledge of the latter is essential if the relationshipbetween these and other clinical variables e.g. babies birth weight is to beinvestigated
During the pilot study 24 hour weighed diet records and minute by minuteactivity diaries were kept by all subjects for 14 days (including 4 weekenddays), and anthropometric measurements were recorded at the beginningand end of the experimental period. Resting metabolic rate and energyexpended during all usual activities was measured using standardprocedures 27'28 . The 24-hour activity diary combined with energyexpenditure measurement for all usual activities is a well tested method ofassessing energy expenditure and has been used extensively in overseasstudies 2830
IIIIIIIIIIII
12
The results showed that 200 subjects measured for 8 days were necessaryto accurately assess mean group nutrient intake. In addition 8measurement days were required to characterize individual energy intake,and 3 measurement days: energy expenditure 25 ' No significantdifference was found between weekday and weekend energy intake andenergy expenditure. However as many overseas studies have found asignificant difference between weekday and weekend energy intake, dietarydata collection periods were designed to include each day of the week2'26.
3.12 Questionnaire PilotTwo questionnaires were tested. The first questionnaire was to determinecultural, social and lifestyle details, and the second to record birth details.The questionnaires were constructed by two graduate womens' studiesstudents. They were scrutinized by members of the local Womens' HealthCollective and subject to intensive peer review by a panel of MasseyUniversity researchers active in this field (i.e., Professor P. Spoonley,Sociology, Ms J. Clare, Nursing Studies, Dr C. Briar and Ms C. Cheyne,Social Policy and Social Work and Ms A. Beasley, Social Anthropology).The applicant and two other interviewers then tested the questionnaires on4 different pregnant subjects (12 in all). The interviewers discussed theirfindings with Professor P. Spoonley and necessary adjustments were made.A further trial with 2 subjects revealed no problems.
3.2 TECHNIQUES OF DATA COLLECTION
3.21 Anthropometric MeasurementsWeight was measured on quality portable bathroom scales, calibratedweekly against a Sauter platform scale accurate to 200 kg ± 0.02 kg.Height was measured with a portable stadiometer. Triceps, biceps,subscapular, costal, suprailiac, mid thigh and knee cap skinfolds weremeasured using Harpenden-Holtain calipers according to the proceduresset out in Gibson28.
3.22 Assessment of Energy and Nutrient IntakeAll food and drink consumed were first weighed on a Salter MicrotonicElectronic Scale with taring facility. Food details and weights wererecorded in special 4 day diet record books given to each subject. The 8day record required was split into 2 four day periods 8 days apart, so eachweekday was represented. This is an acceptable procedure and improvessubject co-operation25.
3.23 Assessment of Activity During PregnancyThe assessment of energy expenditure during pregnancy is complicated notonly by increasing body weight, but also by changes in metabolic rate insome subjects'"'. Hence 24 hour records of physical activity only werekept in special pocket-sized activity diaries with one page for each hour, asquare for each minute, and 10 minutes to a line.
13
3.3
3.24 Questionnaires to Determine Cultural, Social and Birth DetailsThe two questionnaires developed in the pilot were used. On the first visitto each subject their responses to the cultural, social and lifestylequestionnaire were obtained. A few selected questions on personal wellbeing from this questionnaire were asked at the beginning of each of the 3subsequent data collection periods. The short after birth questionnaire wasadministered 2 months after birth. Details of infant development wererecorded at six months and 12 months after birth.
DATA COLLECTION PROGRAMME
4th month pregnancy
5th month pregnancy
7th month pregnancy
9th month pregnancy
2 months after birth
6 months after birth
1 year after birth
8 days weighed diet records3 days activity diariesHeight, weight, skinfoldsQuestionnaire
Well-being questionnaire
As for 4th month pregnancy
Well-being questionnaire
Weight, skinfolds,Birth questionnaire
Weight, skinfolds, questionnaire
Weight, skinfolds, questionnaire
3.4
Each subject was visited at the beginning and end of the 4th and 7th month datacollection period. Answers to 5th and 9th month questionnaires were obtainedwhere possible by phone. After birth data was collected in single short visits.Thus each subject was visited 7 times in the course of the study by the sameinvestigator. (Each subject was always visited by the same investigator).
Data collection from all 197 subjects was completed by April 30 1996.
ETHICAL APPROVALEthical approval for this study was obtained from:
(a) Massey University Human Ethics Committee
(b) Manawatu - Wanganui Area Health Board
140
3.5 SUBJECTSOver 2000 women pass through the ante-natal clinic at Palmerston North Hospitaleach year, of whom —500 are from outlying areas with special obstetric problems.All local general practitioners, midwives, Plunket centres, parents centres,kohango reo, kindergartens, creche, community health centres, the WhareRapuora at Palmerston North Hospital, Linton Army Camp, supermarkets andlibraries were visited every 3 months and asked to display survey publicitymaterials. The area from Bulls to Levin was covered. At intervals notices werealso inserted in community newspapers and read over the local radio communitynews. Potential volunteers contacted the applicant/assistant by phone. A detailedaccount of what was involved in the survey, the feedback each volunteer wouldreceive and a consent form were sent through the post to each potential volunteer.Only those that completed the consent form were used as volunteers. Womenwith a record of chronic disease e.g., hypertension, heart or kidney disease orhistory of obstetric problems were not used.
Two hundred and fourteen women volunteered for the study, 10 miscarriedand 7 withdrew. The volunteers (with and without children) were agedbetween 18 to 35 years, the age range associated with least maternal risk38.Subjects came from all socio-economic levels with 89.9% being of Europeanorigin and 6.6% Maori.
3.51 SUBJECT FEEDBACKAs data collection up to 2 months after birth, coding and preliminary dataanalysis was completed, each subject was sent a detailed analysis of theirdiet, physical activity and body composition changes. All women havereceived their personal analysis. In addition when data collection for allsubjects is completed, all subjects will be sent a summary of the studyresults.
5
[II4. Clii IL/Wit & SOCIO-ECO,Vo f/C 84 CKGROL/fluf) OF SUBJECTS
4.1 RESULTSThe subjects ethnicity is shown in Table 1, and the household compositionincluding total number of incomes coming into the household is shown in Table 2.Table 3 provides information on the living situation of the subjects i.e. whetherthey were partnered, and their husband/partners work situation. The educationalbackground of the subjects is shown in Table 4 and the socio-economic status ofthe subjects and their husbands/partners is in Table 5. The Elley-Irving Sca1e394°was used to determine socio-economic status, with I indicating those of thehighest socio-economic status and 6 those of lowest status. The reported smokingand alcohol consumption levels are shown in Table 6. Finally the physical activitypatterns of the mothers as calculated from their activity diaries are shown in Table7. The sit/stand category was entirely stationary activity, whilst the stand/walkcategory covered activities where subjects mixed stationary activities withmovement e.g. dressing, cooking a meal, laboratory work. The work/houseworkcategory included all other moderate energy expenditure activities as well, and thesport category included other heavy energy expenditure activities.
Table 1:Ethnicity of Subjects
Subjects Ethnicity Percentage
n=197 of SubjectsEuropean New Zealander 89.8Maori 6.6
Pacific Island Polynesian 0Chinese 0Indian 0.5
[Other 3.0
Table 2:Household Composition and Incomes
Household Composition and Incomes(Number in Each Classification)
___:i:n________________n=197
0123456789Total Number Household-160724611321
Total Number of Children73713710311---
Total Number of Pre-School8481301------Children
Total Number of Incomes-481232132----Per Household
II[II[UIIII11Ii'
160
Table 3:Living Situation
Living Situationn=197
Subjects with Husbands
Subjects with Partners
Solo Parents
Subjects not working nor on a benefit
Subjects in part-time or seasonal work
Subjects in full time work
Subjects on dole or domestic purposes benefit
Husbands/Partners in full time work
Husbands/Partners in part-time work
Husbands/Partners on a benefit
Percentage ofTotal Subjects
81.2
12.2
6.6
23.9
37.1
28.4
10.6
85.8
2.0
6.1
Table 4:Educational Background of Subjects
Percentageof Subjects
Two or less years at secondary school
5
Three years at secondary school
19
Fours years at secondary school
34
Five or more years at secondary school
41
Attended Polytechnic 28
Attended University 36
Table 5:Socio-Economic Status of Subjects and their Husbands/Partners
Socio-Economic Status of Subjects and their Husbands/Partners(Number of People in each Classification)
Ellev-1rvi&Scale123456BenefitNo Income
no.no.no.no.no.no.no.no.Subject duringpregnancy 222745201052147
Husband/Partner48 1 32 L2.43 1 961301 / subjects had 110 /lusha/ldJparZl)er or the occupation of the husband/partner was unknown.
17
Non-smokers during pregnancy
Smoked less than 5 cigarettes/day
Smoked less than 10 cigarettes/day
Smoked less than 20 cigarettes/day
Non-drinkers before and during pregnancy
Non-drinkers during pregnancy only
Drank much less during pregnancy
Drank less during pregnancy
Drank more during pregnancy
Percentageof Subjects
91
4
3
24
51
13
12
0.5
Table 6:Lifestyle Behaviours
Table 7:Physical Activity Levels of Mothers (Hours:Minutes)
Sleep/Lie
Sit/Stand
Stand/Walk
Walk/Housework etc.
Sport etc.
Fourth MonthMean Time (SE
10:21(1:41)
9:36(2:14)
1:18(1:41)
2:25(1:45)
0:19(0:31)
Seventh MonthMean Time (SD
10:37(1:53)
9:29(2:26)
1:28(1:50)
2:10(1:41)
0:11(0.23)
4.2 DISCUSSION OF RESULTSIn the geographical area covered by the study, II % of women in the 18 to 35 yearold age group studied were classified as Maori in the last census. Considerablyfewer of the subjects in the study were Maori than could have been expected if arandom sample had been taken. However this study did not target a particularethnic group; ethical committee stipulation meant that subjects could not beapproached by the data collectors themselves, but had to contact the collectorsand volunteer themselves after learning of the study from the publicity materialdistributed throughout the community.
8
The household size varied considerably. One women lived alone, most householdscomprised three people, but some households included up to nine people. Anumber of the larger households included flatmates, boarders, or relatives. Thirty-seven percent of the subjects had no children and most were pregnant for the firsttime. The remaining subjects had up to six children; 56% of subjects having up tothree pre-schoolers. Most of the subjects were married (81.2%) with 12.2% livingwith partners and 6.6% being solo mothers.
By far the greatest number of households had two incomes coming in (62%), withonly 24% being single income households. In at least 13% of households fromone to three incomes came from other family members, relatives, flatmates orboarders, who also lived in the home. An income was counted as money cominginto the home from paid work and/or benefits.
When it came to differentiating between income from paid work and income frombenefits (not counting family support), most of the subjects received income frompart-time, 37%, or full time, 28% paid positions. Ten percent of subjects were onthe dole or domestic purposes benefit, while 24% received no income from anysource i.e. they were supported by their husband/partner. By far the majority ofhusbands/partners were in full time work, with only 6% being on benefits or ACC.
The level of education amongst the subjects was high with 64% having attended atertiary institute of some type. This was reflected in the socio-economic status ofthe 129 subjects who worked. Seventy-two percent of these were classified asbeing in the higher socio-economic groups one to three. More husbands/partners(59%) were also in the higher socio-economic groups one to three.
Most subjects altered their smoking and alcohol consumption during pregnancy,with only 9% of subjects acknowledging smoking, and 25% of subjectsacknowledging drinking during pregnancy. Seventy-five percent of subjectsdeliberately did not drink or reduced their alcohol intake during pregnancy.
There, was a tremendous variation in activity levels with some women keeping uphigh levels of heavy physical work throughout pregnancy, whilst others wereextremely sedentary. On average the women only spent four hours per day in thefourth month and 3.5 hours per day in the seventh month on non-stationarymovement e.g. walking.
There was no significant difference between activity levels in the fourth andseventh months of pregnancy.
5. BODY WI16/IT & BODE FAT LEVELS OF SUBJECTS
5.1 METHODS OF ANALYSISStandard statistical calculations as well as lowess plots and cluster anal ysis ofmu1tvariate observations using Ward's linkage with euclidian distance metricbased on the unstandardised weight chan ges or weight or skinfold proiiies were
9
used to analyse the data. Lowess plots show the individual data points with acurve indicating the smoothed averages. Cluster analysis groups subjects with asimilar profile together. In addition curves showing data in deciles according tomonth were produced using a general linear model with the interaction of twofactors; decj]e indicator and month.
5.2 RESULTSThe mean age of the women in the sample was 29.3 years, standard deviation 4.4and their mean height was 164 centimetres, standard deviation 6.5, range 149.5 to182.7cm.
Table 8:Description of Subjects: Anthropometry
No. of Weight BMI Skin Fold (mm)Subjects
Mean SDRange Mean SDRangeMean SD RangeBefore 19763.012.0 45.0-136.023.44.217.0-50.2---pregnancy**
Month 419767.412.7 47.1-135.524.94.118.1-40.01224551-282pregnancy
Month 7195*73.912.5 51.3-133.027.34.020.0-41.51344468-288pregnancy
Month 2 after190*68.212.8 47.0-125.025.44.518.5-46.21244556-273birth
Month 6 after179*65.913.8 41.0-130.224.55.015.8-48.11134940-281birth
Month 12 after156*65.313.8 46.0-128.824.34.916.5-47.61064539-258birth* ------------- -- -- - - - - - - .----)(J!'•. .(.L4C5L.fl LCJ' The pre-pregnancy weight was self reported
The mean, standard deviation and measurement range for weight, body mass indexand sum of the skinfolds at the measurement intervals throughout the study areshown in Table 8. A box plot of the weight changes with time is shown in Figure1. The bottom of the box is the lower quartile, the line across the box is themedian and the top of the box is the upper quartile. The lines extending above andbelow the box show the range within statistical limits. The asterisks portrayoutliers. There was a group of tall big women who comprised the outliers groupin most graphs of the anthropometric data. Figure 2 shows the weight changeswith time when the women are grouped in deciles according to their stated pre-pregnancy weight. The mean total sum of the skinfolds at each measurementinterval is shown in Figure 3 along with the standard error of the mean. Fi gure 4shows the mean weight profile when women with similar patterns of weightchan ge are clustered together. Figure 5 shows the mean skinfold profile whenv omen with similar skinfold profiles are clustered together. Jr each of these
IIIIIIIa
10
figures the tall big women mentioned above are found in the highest group. Itshould be noted that weight before pregnancy was not measured, but recalled bythe subjects.
Box Plots of Weight Versus Month
130 ***
120* *110 **
*0) 100
* **
900)a)
70
60
50
40
OM3nths 4vtnths Months 2D.PP 6Mo.PP 12Mc.PP
Month From Conception
Figure 1
From the outset the biceps and costal skinfolds showed more variation with time,when compared with the other skinfolds measured, that is, they were the skinfoldsmost affected by pregnancy. In the analysis to determine the influences onbirthweight, weight at one year, and maternal weight loss after birth, the bicepsand costal skinfolds at four months have proved significant. The average bicepsand costal profile together with the percentage of total skinfolds contributed bythese two skinfolds over time is shown in Figures 6 and 7.
5.3 DISCUSSION OF RESULTSThe body weights and BMI's of the subjects ranged from measurements thatwould be classified as extremely lean and indicating possible malnutrition to thoseindicating obesity. The average weight gain to month seven of pregnancy was10.9kg, but varied widely from -4.7kg to 25.0kg.
Few women returned to their pre-pregnant weight after birth. On average at 12months after birth the women were still 2.3kg heavier than before pregnancy andthis was reflected in the higher mean BMI at this time. When we grouped thewomen in deciles according to their pre-pregnancy weight, the heavier women puton the most weight after birth (top two deciles labelled 8 and 9). Only 20% of thewomen (in the deciles labelled 6 and 7) returned to their pre-pregnant weight (seeFigure 2). The mean skinfold profile with time clearly shows the increaseddeposition of fat during pregnanc y and mirrors the weight changes (see Figure 3).
11
135
-
0E=
C/)Co
F2
0.
05
Average Weight Profiles According to MonthGrouped By Deciles Of Stated Pre-Pregnancy Weight
100
90
U)
-cc,)
-+- .---0 60-- —- --
50
0 10 20
MonthDeciles: 0= smallest 0-10%, 1= 11-20%, etc.
Figure 2
Average Ftofile For Total Skinf olds
00er +1X2*3
06
4Months 7Months 2Mo.PP 6Mo.PP QMo.PP
:)nth ofstation/ Rstpartum
Figure 3
12
When the weight change over time was subjected to cluster analysis (see Figure 4)four distinct weight profile groups emerged.
A high initial weight group that gained weight till the seventh month and lostit very slowly after birth (4 on the graph).
A moderately high initial weight group that did not gain any weight before thefourth month, and after an initial loss in weight after birth began to gainweight again (1 on the graph).
•A moderate initial weight group who gained the most during pregnancy(-15kg) then lost weight steadily after birth (3 on the graph).
•A low initial weight group who almost returned to their pre-pregnant weightafter birth (2 on the graph).
A'..erage Weight Profiles by MonthGroups As Given By Cluster Analysis of Weight changes
0175 - +2
*470
--.3-4
/\,i.
I
x4'-
o 11) 20
Fvbnths
Figure 4
A similar cluster analysis (see Figure 5) on the sum of skinfolds with time,revealed three profiles showing a similar trend with time (1, 2 and 3 on the graph).Here the skinfolds increased to the seventh month and decreased with time. Thesegroups differed mainly in their skinfold thickness. The highest fatfold group (4)showed little increase during pregnancy.
13
riB
Y 12.8
118
CD 10.8
9.8
Aerage Skinfold Sum Profiles by Month -Groups As Given By Ouster Analysis of Skinfokis
250
150
E
0 i+ 2
-34
-
50
5 10 15 20
nths from Concepon
Figure 5
Both the average biceps and costal skinfolds showed an increase during pregnancyfollowed by a decrease after birth. However when these individual skinfolds areconsidered as a percentage of the sum of skinfold measurements at each datacollection interval, their contribution to the sum of the skinfolds does not remainconstant with time. The contribution from the costal skinfold decreases from thefourth month, indicating that this skinfold becomes relatively small with time,whereas the contribution of the biceps skinfold is very variable with time (seeFigures 6 and 7).
Average Biceps Profile
4Months 7Moriths 2Mo.PP 6Mo.PP QMo.PP
vbnth of Gestatioc-i/ Fbstpartum
Figure 6(a)
14
21
F317
cu16
14
Average Cc)stal R-ofile
4Months 7Months 2Mo.PP 6Mo.PP 2Mo.PPMnth of GestatiorV fstpartum
Figure 6(b)
Biceps Profile (% of Total Skinfolds)
1D.O I IC')
I I9.5-
U-C/)a Ia)
9.0-
IIII4Months 7Months 2Mo.PP 6Mo.PP 12Mo.PP
Mrnth of GestatiorV Postpartum
Figure 7(a)
U
U
U
U
U
U
U
UFigure 7(b)
16. DIETARY Ito/TAKE OF THE SUBJECTS
6.1 METHODS OF ANALYSIS UThe latest update of Diet I (Version 4 with OCNZ96) was used to calculate the nutrientintake for each woman from the eight days weighed diet record in the fourth month, andthe eight days weighed diet record in the seventh month. Standard statistical techniquesand the Minitab 10.5 Statistical Programme were then used to analyse the data.
U6.2 RESULTS
6.21 Energy IntakeThe mean energy intake and a description of the energy sources in the fourth andseventh month are shown in Tables 9 and 10. Histograms showing the distributionof individual total energy intake in the fourth month, and again in the seventhmonth are shown in Figure 8. Additional histograms showing the distribution ofindividual percentage total energy from fat and carbohydrate and in the fourth andseventh month are shown in Figure 9.
U
U
4000600080001000012000140001600018000
4000600080001000012000140001600018000Energy (kJ) - 4th rronth
- - -Quartile
300050007000900011000130001500017000
300050007000900011000130001500017000Energy (kJ) - 7th month
Figure 8Distribution of Total Energy Intake
17
30U)
2015CQ)0
10
0
0
30
Cl)
20C,)0Ca)E10
El4th month 7th month El
80 - 70- -
70 60 [II60 -50 -
40_ Ii130 p30-20 - 20 _10 - 10 -
0IIIIII II I354045505560 25303540I
45505 I 560% of total energy from carbohydrate % of total energy from cathohdrote U
El4th month 7th month U
90- 80 -
80 70 -
70 - 60>60 -
50 >50 -
40 o.- U10 -20 - 20 -10 -0-I
II I I I253035404550 253035404550I
5I5% of total energy from fat % of total energy from fat ElUFigure 9
Distribution of the Percentage of Total Energy from Carbohydrate and Fat UUUElU
_________ El18 U
Table 9:Description of Energy Sources in the Fourth and Seventh Month of Pregnancy
EnergySources in the Fourth Monthn=197 MeanStandardLowerUpperMin.Max.
DeviationQuartileQuartile
Total energy (kJ) 8897.2086.7635.10421.3821.18617.
%of total energy from protein14.22.212.715.78.222.4
% of total energy from total fat35.64.432.738.623.448.4
% of total energy from carbohydrate50.14.846.853.434.764.2
% of total energy from alcohol0.20.50.00.00.03.6
EnergySources in the Seventh Monthn=193 MeanStandardLowerUpperMm.Max.
DeviationQuartile Quartile
Total energy (Id) 8903.2225.7414.10505.3247.16561.
% of total energy from protein14.42.512.515.87.922.1
% of total energy from total fat36.04.532.739.023.354.0
% of total energy from carbohydrate49.55.246.252.926.561.3
% of total energy from alcohol0.10.30.00.00.03.0
19
Table 10:Further Description of Energy Intake -
Fourth MonthSeventh MonthNutrition -Mean (SD)Mean (SD)Task Force
RecommendationsPercentage of total energy from22.8(8.5) 22.6(8.7) 15soluble sugars -
Percentage of total energy from16.8(5.4) 16.8(4.9) 8-12SFA
Percentage of total energy fromMUFA
11.8(3.5) 11.9(3.5) 10.20
Percentage of total energy from4.2(1.7) 4.3(1.8) 6-10PUFA
PIJFA & MUFA/SFA ratio 0.95 0.97 1.8-3.2
U6.22 Mineral and Nutrient Intake UThe mean, median, standard deviation, upper and lower quartile and range of all
nutrient intakes is shown in Table 11 for the fourth month of pregnancy and Table12 for the seventh. Histograms showing the distribution of nutrient intake, areprovided for all major nutrients at month four and month seven of pregnancy inAppendix One. The mean, upper and lower quartiles and the Australianrecommended nutrient intake for pregnant and non- pregnant women are shownon all histograms.
UUUUUUU
- U20U
Table 11:Descriptive Statistics of Nutrient Intake for the 4th Month.
Variable (n=197) Mean MedianStandardMm.Max.LowerUpperDeviation QuartileQuartile
Protein (g) 76.276.4917.4229.95150.465.4686.93Total fat (g) 86.2883.5124.7734.76208.968.15101.93Carbohydrate (g)276.39272.1869.44103.56581231.28319.31Alcohol (g) 0.53101.52011.700Total sugar (g)128.56122.8748.231.71431.897.4155.67Glucose (g)22.92922.259.074.8450.516.529.03Fructose (g) 19.4318.818.792.1848.513.2624.59Sucrose (g) 61.7158.6132.4211.01360.742.3373.58Lactose (g) 14.73913.777.871.67469.2518.77Maltose (g)2.62842.461.240.397.11.763.29Starch (g) 143.66141.6836.5455.18240.6117.24165.37Dietary fibre (g)22.73922.176.786.2144.218.4526.89Cholesterol (mg)289.25272.9190.5996.47541.4229.75351.3Sat. fat (g) 39.53737.8312.8315.18115.131.1946.53Mono, fat (g)27.75927.768.2211.269.121.833.31Poly. fat (g) 9.9769.394.012.6927.17.2811.793carotene(pg)303027711706294944416534018Retinol (g) 510.6443.5402.3172.94666.9356.2575.9Total Aeg. (jig)1017.4936.4519.4316.15160.6694.11251.9Vitamin C (mg)116.59106.3563.8217.9440767.98151.58Vitamin D (jig)1.21970.950.90.0350.551.68Vitamin E (mg)8.7288.422.973.0421.76.610.49Thiamin (mg)1.5161.50.420.5231.231.77Riboflavin (mg)1.75381.720.540.533.81.372.03Niacin eq. (mg)30.78330.527.1613.7353.725.9935.03Vitamin B6 (m2)1.46621.430.490.544.41.151.75Vitamin B12 (jig)4.1533.582.91.3734.72.944.63Pantoth.acid (rug)4.65894.531.23293.895.35Biotin (g) 33.79132.7612.7611.5695.925.7739.39Total folate (4g)240.86232.4893.9683.111062.3187.89275.51Sodium (mg)32603098.4971.61337.36726.32571.13730Potassium (rug)3132.33180.6794.21133.15640.52525.73682.5Magnesium (mg)284.3275.6181.92119.54694.2230.73332.72Calcium (mg)827.3810.6295.4271.41895621.5982.4Phosphurus (mg)1329.21340.6346.2503.12456.41091.71540.7Manganese (jig)4384415916199691036030975518Iron (mg) 11.27110.992.93520.89.2112.83Zinc (mg) 10.15910.252.54.7219.48.3911.77Sulphur (mg)831.8822.7188.1367.41655.1699.9962Chloride (rug)50524753163020931160440365909'Copper (mg)11.42441.380.520.544.71.11.62Selenium (j.ig)36.7732.6320.059.75139.323.0742.57
21
Table 12:Descriptive Statistics of Nutrient Intake for the 7th Month.
Variable (n=193) Mean Median Standard Mm.Max.LowerUpper
Deviation Quartile QuartileProtein (g)77.6476.5120.3222.85151.263.4988.23Total fat (g)86.9484.3324.5828.21169.3 - 69.58102.85Carbohydrate (g)273.94270.9876.9492.7591.5222.46324.38Alcohol (g)0.3901.109.100Total sugar (g)128.08121.0849.4417.53335.292.68159.09Glucose (g)23.2622.5210.843.2255.714.8129.35Fructose (g)19.717.6510.391.755.812.326.36Sucrose (g)59.8756.0827.794.68182.141.2476.03Lactose (g)15.6714.718.6043.49.8619.41Maltose (g)2.522.281.240.037.31.673.27Starch (g)141.81139.2739.8654.69 _270.2113.49165.02Dietary fibre (g)23.4522.877.35.7350.118.4328.11Water (g)1317.71280.9451.5470.7 2587.5950.21609.8Cholesterol (mg)294.72 280.24105.7672.08782.7226.89 - 340.96Sat. fat (g)39.5537.5511.6811.0673.131.4948.57Mono. fat (g)28.1227.598.299.8658.221.9333.15Poly. fat (g)10.169.354.323.0827.26.9712.27j3carotene(ig)3007286716511111245618123723Retinol (g)532.4461.5470.9129.5 5722.8357586.6Total A eq. (p.g)1035.2983.9551.6176.1 6290.9777.9 - 1192.6Vitamin C(mg)117.02106.7470.524.56413.967149.42Vitamin D(j.tg)1.31.180.88 -040.61.81Vitamin E(mg)8.688.443.272.8622.66.3710.48Thiamin (mg)1.521.460.460.553.31.191.8Riboflavin (mg)1.811.690.60.563.61.372.16Niacin eq. (mg)31.5331.628.429.772.125.735.94Vitamin .B6(mg)1.581.55 10.590.434.91.181.9Vitamin Bl2(p.g)4.213.622.770.8226.82.944.87Pantoth.acid (mg)4.714.611.351.5812.43.885.45Biotin (g) 33.3232.0812.1610.4481.624.3641.49Total folate(p.g)241.33236.0976.271.23483.3184.93290.17Sodium (mg)_31663035.11007.1986.2 7710.42489.73795.7Potassium (mg)31583157879.3916.5 6327.825893711.6Magnesium (mg)291285.6987.3597.9623.4234.18341.77Calcium (mg)858.2830.6316.1162.2 1847.3634.51036.9Phosphurus (mg)1353.71326.1373.8414.7 2600.71072.21592.9Manganese (jig)45404517171413441023532035710Iron (mg) 11.4911.253.083.9222.39.3513.61Zinc (mg) 10.2710.242.922.5224.78.33 - 11.93Sulphur (mg)842.7833.4208.7235.6 1597.2695.8949.9Chloride (mg)48804603171614421377936865785Copper (mg)1.381 .360.420.453.71 .1 1.62Selenium (tg)1_36.2431.1519.417.11 1 122.823.06 - 43.88
III220
IIUI
6.23 Significant Differences in Nutrient Intake Between the Fourth and SeventhMonths of PregnancyTable 13 reports the results of student T tests used to determine whether therewas any significant difference between the nutrient intake in the fourth and seventhmonths. Only Vitamin B6 had a P-value<0.05, i.e. a significant difference inintake.
Table 13:Difference Between the 4th Month and 7th Month Nutrient Data.
VariableP-valueVariableP-valueProtein 0.29 Vitamin 0.71Total fat 0.48 Thiamin 0.88Carbohydrate 0.70 Riboflavin 0.19Alcohol 0.25 Niacin eq. 0.18Total sugar 0.81 Vitamin .B6 0.0029Glucose 0.65 Vitamin B12 0.86Fructose 0.66 Pantoth.acid 0.52Sucrose 0.66 Biotin 0.38Lactose 0.088 Total folate 0.90Maltose 0.27 Sodium 0.20Starch 0.42 Potassium 0.77Dietary fibre 0.18 Magnesium 0.12Cholesterol 0.48 Calcium 0.15Sat. fat 0.71 Phosphurus 0.32Mono. fat 0.34 Manganese 0.097Poly. fat 0.43 Iron.. 0.17f3carotene 0.68 Zinc 0.68Retinol 0.64 Sulphur 0.45Total A eq. 0.85 Chloride 0.19Vitamin C 0.85 Copper 0.29Vitamin D 0.29 Selenium 0.81
6.3 DISCUSSION OF RESULTS.
6.31 Energy IntakeThe mean energy intake of 8.9MJ/day in the fourth and seventh months ofpregnancy equated with the British Reference Nutrient Intake of 8.9MJ/day, butwas slightly less than the Australian Recommended Intake range of 9.35 to10.8MJ/day 41 . One quarter of the subjects had energy intakes of 10.4MJ/day orgreater in , the fourth and seventh months of pregnancy, with some very highintakes being recorded (see Figure 8). While the energy intake of most subjectswas adequate, of real concern where the 20% of subjects who consumed:5;7.0MJ/day in both the fourth and seventh months. Whilst under-reporting wasprobably the cause in some cases, the comments of the data collectors indicatedthat inadequate food Stores was the reason for many of these low intakes.
123
There was no significant difference (p0.42) between the energy intake in thefourth and seventh months. This is in line with the work of Durnin and hislongitudinal five country study on the energy requirements of pregnancy who alsofound this same result. Thus voluntary energy intake does not appear to increaseas pregnancy progresses.
The mean percentage of total energy from protein, fat and carbohydrate in thesewomen's diets was close to the Nutrition Task Force 42 recommendations.However when broken down further as in Table 10, the mean percentage of totalenergy from soluble sugars is 7% higher than the Task Force recommendationsand the proportions of total energy from saturated fatty acids is also higher thanrecommended.
6.32 Mineral and Vitamin IntakeDietary intake of most nutrients was adequate in this study. However the intakeof a number of minerals was less than two thirds of the Australian RecommendedNutrient Intakes (RNI)4 ' for a substantial proportion of subjects as shown in thetable below. The Australian RNI for iron is generous compared with that of othercountries, and the scientific basis for the selenium and zinc RNI could bequestioned. However there is a real concern regarding the mineral intake of anumber of subjects in this study.
Table 14:Nutrients below two thirds of the Australian RNI in a substantial percentage ofsubjects in the fourth and seventh months of pregnancy 0
NutrientTwo ThirdsPercentage ofRNI Subjects
Calcium 726mg 30Iron 14.5mg 80Zinc 10.6mg 60Selenium 53pg 80Folate 264jtg 75
A substantial proportion of these women apparently also had very low folateintakes. Again the basis for the RNI for folate as well as the analytical figures forfolate in foods could be questioned, but when the connection of neural tubedefects with low folate levels in early pregnancy is considered, this finding is aconcern.
The intakes of only two nutrients could be considered excessively high. Thesewere firstly retinol equivalents, where 80% of subjects had intakes greater than theAustralian RNI's and 20% of subjects had intakes more than twice the RNI's.This finding is of concern considering the possible supplementation of NewZealand foods with carotene and vitamin A as a result of the harmonization withAustralia of our food regulations. Excessive vitamin A intakes may have ateratogenic effect on the foetus. Secondly 80% of subjects had vitamin C intakes
IIIIIIIIUIIIIIIIUI
24
11
greater than the Australian RNI's, 40% of subjects had intakes more than doublethe RNI's and 20% of subjects had intakes more than triple the RNI's. These highvitamin C intakes were largely the result of high fruit juice consumption. Asvitamin C is water soluble these high intakes are unlikely to present a problem.
Protein intake in terms of g/kg of pre-pregnant body mass are shown in the tablebelow.
Table 15:Protein Intake ('g/kg Body Mass)
MeanSDQi03Mm.Max.Fourth Month1.150.310.951.340.432.43Seventh Month1.080.33 1 0.881.230.322.87
Twenty percent of subjects had protein intakes below the recommended level of0.8gfkg of body mass. A small percentage of women has excessively high proteinintakes.
Animal protein intake was high and 40% of subjects had cholesterol intakes above300mg/day. In contrast fibre intake was low with 40% of subjects consuming lessthan 20g of dietary fibre a day and only 10% consuming more than 30g of fibre aday.
6.33. Significant Differences in Nutrient Intake Between the Fourth and SeventhMonths of PregnancyApart from vitamin B6 (p=0.0029) there was no significant difference between theintake of any other nutrients in the fourth and the seventh months of pregnancy.
7. EFFECT OF SOCIO-ECONOMIC GROUP ON DIETARY Its/TAKE OFTHE MOTHER, & ,INTHROPOiWETRIC ME4SUREMEATS OFMOTHER AND BABY
7.1 METHOD OF ANALYSISUsing the Elley-Irving Index the women were grouped from one to six according tosocio-economic Status of their husband/partner; one being the highest and six being thelowest socio-economic group. Student's T-Test and the Wilcoxon Rank-Sum Test (anon-parametric equivalent of the T-Test) were used to determine if there were anysignificant differences between extreme high and low SES groups in dietary intake of themother and anthropometric measurements of mother and baby. Here high was SESgroups I and 2 combined and low was SES groups 5 and 6 plus husband/partner on abenefit as well as those subjects with no husband/partner.
A similar anal ysis was carried out comparing those subjects whose sole source of incomewas the dole or domestic purposes benefit, with rest of the sample.
125
7.2 RESULTS
Student's T and the Wilcoxon test gave similar results in both analyses. Only theStudent's T Test results will be reported. Significant differences in major nutrient intakeat the fourth month of pregnancy between socio-economic groups (I and 2) and (5 and 6)are shown in Table 16. The picture was similar for dietary intake in the seventh month.
Significant differences in major nutrient intake in the fourth month between subjects on abenefit and the rest of the sample are shown in Table 17. Similar results were seen in theseventh month with significant differences found in energy, carbohydrate, iron, vitamin Cand saturated fat as well.
7.3 DISCUSSIONS OF RESULTSThe major finding from this analysis was that there is a significant difference in the meanweight of food eaten by Group One and Two (1 864g), Group Five and Six (1 680g) andthe Benefit Group (1 570g). This has an across the board significant impact on the intakeof most nutrients. Where there is a significant difference in nutrient intake, Group Oneand Two intake is always the highest, Group Five and Six is always lower and the BenefitGroup is always the lowest, in all cases regardless of nutrient type. Hence the poorergroups are eating significantly less leading to a significantly lower intake of mostnutrients.
However when the mean vitamin and mineral intakes of these lower socio-economic andbenefit groups were compared with the Australian RDI's, only five nutrients; calcium,zinc, iron, selenium and total folate were substantially below recommended intake levels.This comparison is shown in Table 18 below.
126
Table 16: Socio-Economic Group and Dietary Intake at the Fourth Month of Pregnancy -Significant Differences Only
Nutrient Group 1 & 2Group S & 6 *P-valuen=80 n=45
Mean (SD)Mean (SD)Weight of Food (g) 1864(471)1680(505)0.024
Energy (kJ) 9233(1954)8294(2472)0.016
Protein (g) 80(17) 71(17)0.003
Carbohydrate (g) 280(62)248(81)0.014
Starch (g) 153(35)131(32)0.0003
Fructose (g) 23(10) 19(9)0.006
Glucose (g) 23(8) 18(8)0.006
Fibre (g) 24(7) 19(7)0.000
MUFA (g) 31(8) 28(10)0.049
PUFA(g) 12(4) 10(4)0.018
Cholesterol (g) 314(95)273(86)0.007
Calcium (mg) 945(341)785(268)0.002
Iron (mg) 12.8(3.1)10.8(3.2)0.0005
Zinc (mg) 10.8(2.5)9.1(2.1)0.0001
Sodium (mg) 3360(871)2690(671)0.0000
Retinol (p.g) 579(585)388(141)0.003
J3-Carotene (p.g) 3922(1854)3238(1779)0.022
Vitamin E (mg) 9.9(3.2)7.7(3.0)0.0001
Thiamine (mg) 1.4(0.3)1.2(0.4)0.011
Riboflavin (mg) 1.8(0.6)1.6(0.5)0.021
Niacin Equivalents (mg) 32.3(6.7)28.9(7.3)0.0063
Vitamin B6 (Mg) 1.7(0.5)1.4(0.4)0.0001
Total Folate (fig) 262(119)206(69)0.0006
Vitamin C (mg) 125(66)103(68)0.043
* This group includes 13 subjects whose husband/partner was on a benefit, and 17 subjects who had nohusband/partner, or the occupation of the husband/partner was unknown. Similarly in Tables 18 and 19and in the discussion.
27
Table 17:
Benefit as the Sole Source of Income and Dietary Intake in the Fourth Monthof Pregnancy - Significant Differences Only
Nutrient In WorkBenefit Only -P-valuen=176 n=21
Mean (SD)Mean (SD)Weight of Food (g) 1821(490)1570(462)0.027Protein (g) 77(17) 65(18)0.009Protein (g/Kg of Body Mass) 1.2(0.3) 0.9(0.3)0.0002Dietary Fibre (g ) 22(7) 17(7)0.004Fructose (g) 23(9) 17(9)0.016Glucose (g) 22(8) 17(8)0.010Sucrose (g) 59(27) 42(15)0.0002PUFA (g) 11(4) 9(3)0.013Cholesterol (g) 306(94) 238(65)0.0002Calcium (mg) 895(308)713(232)0.003Zinc (mg) 10.3(2.5) 8.6(2.1)0.002Potassium (mg) 3146(762)2617(900)0.016Sodium (mg) 3175(822)2601(792)0.004Retinol (j.tg) 508(4 15) 322(130)0.0000Vitamin E (mg) 9.3(3.2) 6.4(2.4)0.0000Thiamine (mg) 1.3(0.3) 1.0(0.3)0.0008Riboflavin (mg) 1.7(0.5) 1.4(0.4)0.002Niacin Equivalents (mg) 31.3(7.0)26.5(7.0)0.006Vitamin B6 ( Mg) 1.6(0.5) 1.2(0.4)0.0001Total Folate (.1g) 244(99) 179(45)0.0000
Note: As well as the above there were significant differences between energy, carbohydrate,iron, vitamin C and saturated fat intake in the seventh month in the benefit and in workgroup, (p:!^0.05).
128
Table 18:Nutrients Substantially Below Australian Recommended Nutrient Intake (RNJ)Levels
Nutrient RN! RN!Benefit Group Socio-Economic
WomenWomenMeanGroup 5 & 619-54 yearsPregnant Mean
Iron (mg) 12-16+10-20 10 II
Calcium (mg) 800 1100 713 785
Zinc (mg) 12 16 9 9
Selenium (.ig) 70 80 32 38
Total Folate (fig) 200 400 179 206
Surprisingly there was no significant difference between groups in the percentage of totalenergy that came from protein, fat and carbohydrate. The poorer groups just ate less; theratio of their energy sources remaining the same. The common overseas finding thatlower socio-economic groups eat higher fat diets is not found in this study.
The lower socio-economic group were significantly younger than socio-economic groupone and two (26 years vs 31 years, p=0.0000) and the benefit group were significantlyyounger again than the rest of the subjects (24 years vs 29.5 years, p=0.0000 ). Thebenefit group also smoked significantly more than the rest of the subjects (p=0.0089).However despite this there were not significant differences in weight before pregnancy,weight gain during pregnancy, and weight loss after pregnancy in any of the groups.There was also no significant difference in skinfold measurements at these times.
Table 19: Measurements According to Socio-Economic Class
Benefit GroupRest of SampleP-valueMean:Birthweight (g) 3471. 3572. 0.47Mean:Birth Head Circumference (cm) 35.4 35.0 0.36Mean:Weight at 6 weeks (g) 4888 5001 0.55Mean:Weight at 1 year (g) 9835 12003 0.03
Group s&6Groupl&2P-valueMean:Birthweight (g) 3445 3607 0.15Mean:Birth Head Circumference (cm) 34.8 35.5 0.03Mean:Weight at 6 weeks (g) 4761 5034 0.03Mean:Weight at I year (g) 9956 9891 0.85Mean:Head Circumference at I year (cm) 46.4 47.6 0.01
29
However while there was no signficant difference in birthweight and weight at six weeksin infants born to mothers on a benefit, there was a significant . difference in weight at oneyear. In infants born to lower socio-economic group mothers, there was no significantdifference in birthweight and weight at one year, but a significant difference in othermeasurements. (See Table 19 above). There are obvious negative impacts on growth inchildren born into lower socio-economic level homes. More work needs to be done tofurther quantify this effect.
II11I'IIII
8. FACTORS 11141 IA/FL (lEA/CE THE LOSS OF FAT ACCL/,JIL/L4 TEl)DURING PREGA/AA/C}'
8.1 METHODS OF ANALYSISLinear regression analysis.was used to determine the factors that influenced the loss of fatgained during pregnancy. Special techniques included the careful linear regressionanalysis of individual models, both building up from simple models and simplifying downfrom complex ones produced by stepwise model selection with adjusted r 2 as the selectioncriteria; and Best Subsets regression with adjusted r 2 and Mallows Cp criteria. In additionanalysis of partial residual plots was used to pictorially represent the regressioncoefficients in the full model.
Around 600 variables were considered in the regressions. These included around 52nutrients, around 45 maternal anthropometric measurements and —20 infantanthropometric measurements and development criteria. The remainder were social,cultural, lifestyle and medical variables including extent and severity of morning sickness.
For the purpose of the analysis mother's weight change was defined as the differencebetween the mother's first weight measurement at month 4 of pregnancy and her weightat 6 months after birth. Other measures of weight change were explored but proved lesssatisfactory. The pre-pregnancy weights were self-reported and it was felt that thesewould prove unreliable as a baseline for defining weight change. However weight risefrom pre-pregnancy to month 4 of pregnancy was investigated as a possible covariate.The end point of the study could have been the mother's weight at 12 months postpartum, but a number of subjects had left the Manawatu by this time, and the missingvalues reduced the data set.
8.2 RESULTSThere were 177 women for whom complete data was available for up to 6 months afterbirth. On average these mothers lost 0.81 kg (±5. 1) between month 4 of pregnancy andmonth 6 after birth, with individual values ranging from a loss of -13.5kg to a gain of15.2kg. The extent of this mean weight loss reflects the fact that the women's weightswere above normal by the time of the first interview.
30
60
50
> 40
30
20
ID
0
8C7C6C
'5C4C
LEg
3C2C
130
A histogram showing the distribution of weight changes in the women between month 4of pregnancy and month 6 postpartum is shown in Figure 10. When the differencebetween the reported weight of the subjects before pregnancy and their weight at month 6post partum is investigated on average they gained 3.4kg (5.8) with individual valuesranging from -19.3kg to + 24.7kg. These weight changes are also shown in Figure 10.
Mothers' Weight Changes:4th Month of Pregnancy - 6 Months Postpartum
- 16-2-8-40482Weight Change: 4th month to 6 rronths pp
Figure 10(a)
Mothers' Weight Changes:Pre-pregnancy - 6 Months Postpartum
- '-'I-- LI .J ¼! .J LI LI CVC..)
Weight Change: 0 to 6 rronths pp
Figure 10 (h)
31
Two correction factors; one for gestational age of the foetus at the time of the firstmeasurement; and one for the weight gained by the mother before the first measurementwere derived to optimise description of the data in the linear regression.
Analysis showed that on average mothers started putting on weight at about 13 weeksgestation. This is illustrated clearly in Figure 11 where 13 weeks gestation is indicated bya vertical line. Gestational age was corrected in the model by a piecewise function;
Gest> 13 = 0 (if gestational age :^ 13 weeks)and
Gest> 13 = Gestational Age - 13 (if gestational age> 13 weeks)
In addition, if the mother lost weight in the first trimester this did not seem to influencelater weight change. However if she gained weight in the first trimester this waspredictive of weight change, that is, the more weight gained in the first trimester, themore weight lostpost-partum, though not enough to compensate for this weight gained.This distinct effect is illustrated in Figure 12. As for gestational age, this was correctedfor by using a piecewise linear model where;
Gain W14 = 0 (if weight at month 4 of pregnancy minus pre-pregnancy weight was :!^0),and
Gain Wt4 = weight at month minus pre-pregnant weight (if this difference was positive)
The basic regression model is shown in Figure 13. This model is restricted to only themore highly significant variables. Figure 14 is an extended model which includes someless highly significant variables. This regression is included as it gives some pointers forfurther research and investigation. A summary table (Table 20) shows the build up of theregression models. Tables 21 and 22 provide the 95% confidence intervals, p values andthe percentage of weight change explained by the variables in each of the models.Selected lowess curves, interval and box plots are included in the discussion of results toillustrate the effect of some of the variables on weight change. A lowess curve shows allthe data points and their smoothed average, a box plot shows the median, upper andlower quartile, the range defined by the quartiles and their outliers, an interval plot showsthe mean ± the standard error.
32
Mothers ' Weight Change (Second Trimester to 6 Months PP)Versus Actual Gestational Age At First Interview
Piecewise Model= Constant For Gest.Age<13 wks; Otherwise Regression Line15 -
o- ooo 00
0 0o
000P1,00;Z7, 0) 00)
-
0CD 0 CPO 0
0000
-15
10152025
Gestational Age At First Interview (weeks)o=Data .=Fitted Values (R2=135%) _=Smoothed Average
Figure 11
Mothers' Weight Change (Second Trimester to 6 Months PP)Versus Reported Weight Change Before First Interview
Piecewise Model= Constant If Weight Loss; Otherwise Regression Line15— 0
0L o 0
00
a) 5 -Cz
o 0000
.g) -5 -a)
0-15--i.
-10 0 10
Reported Weight Change Before First Interview (kg)o=Data .=Fitted Values (R2=9.1%) _=Smoothed Average
Figure 12
33
Regression Analysis For Basic ModelThe regression equation isWtChange = - 101 - 0.571 Gest>13 - 0.367 GainWt4 + 12.9 LogSieep - 0.00848 Sip-Stnd
+ 0.0116 Sip-Walk + 0.750 SES.mum + 0.292 BML/4mo + 4.60 BSF/CoSF + 0.522 No.Pregs+ 0.247 Age - 4.08 Smoke? - 4.37 Toxhosp - 1.10 BroknSip + 1.60 Baby Walk + 1.44 Bottlefd- 0.00135 Energy + 0.134 SFA + 0.105 AlcBefor - 1.02 Alcohol + 2.99 Vit.136 + 0.118 Fructose-0.000585 B-Carot
150 cases used 47 cases contain missing values
PredictorsConstantGest>13Gain Wt4LogSleepSlp-StndSip-WalkSES .mumBMJJ4moBSF/Co5FNo.PregsAgeSmoke?ToxhospBroknSlpBaby WalkBottlefdEnergySFAAlcBeforAlcoholVit.B6FructoseB-Carot
Coef-100.680-0.571-0.36712.860-0.0080.0120.7500.2924.5960.5220.247-4.084-4.369-1.1021.5971.441-0.0010.1340.105-1.0202.9900.118-0.001
Stdev14.84000.10450.09512.19200.00340.00370.17620.07811.39700.23640.08111.29501.22800.40980.58910.69600.00040.05860.04180.30380.79460.04980.0002
t- ratio-6.79-5.46-3.865.87-2.493.144.263.733.292.213.04-3.15-3.56-2.692.712.07-3.092.292.52-3.363.762.36-2.36
p0.0000.0000.0000.0000.0140.0020.0000.0000.0010.0290.0030.0020.0010.0080.0080.0400.0020.0240.0130.0010.0000.0200.020
s = 3.394R-sq = 64.8% R-sq(adj) = 58.7%
Analysis of VarianceSOURCE DFSSMSF pRegression222690.70122.30 10.62 0.000Error1271462.7011.52Total1494153.40
Figure 13
34
Regression Analysis For Extended M JelThe regression equation isWtChange = - 67.1 - 0.660 Gest> 13 - 0.424 GainWt4 + 13.2 LogSieep - 0.0122 Sip-Stnd + 0.0165 SIp-Walk
+ 0.281 BMIJ4mo + 7.58 BSF/CoSF + 0.615 No.Pregs + 0.340 Age + 0.344 SES.mum -4.15 Smoke?- 5.20 Toxhosp - 1.00 Brokn Sip + 2.15 BahyWalk ± 0.956 Bottlefd - 0.00647 Energy + 0.122 SFA+ 0.116 AlcBefor - 1.31 Alcohol + 4.16 Vit.B6 + 0.134 Fructose -0.000305 B-Carot - 0.0127 Tot.fol+ 0.222 MUFA + 0.653 Protein - 298 ProtlNrg - 0.607 Zinc + 1.55 PtTmWork - 1.66 GyneOp+ 1.75 Asthma - 3.02 Pain/ab + 1.61 Bleeding + 1.96 UTrctlnf - 1.47 Anaemia
150 cases used 47 cases contain missing values
PredictorConstantGest> 13GainWt4LogSieepSIp-StndSip-WalkBMIJ4moBSF/CoSFNo.PregsAgeSES.mumSmoke?ToxhospBroknSlpBabyWalkBottlefdEnergySFAAlcBeforAlcoholVit.B6FructoseB-CarotTot.folMUFAProteinPro VNrgZincPtTm WorkGyneOpAsthmaPain/abBleedingUTrctlnfAnaemia
Coef-67.13
-0.65953-0.42396
13.235-0.0122490.0164990.281077.5770.61480.340280.3435
-4.148-5.202-1.00262.15450.9564
-0.0064710.121990.11598
-1.30994.16300.13354
-0.0003051-0.0126850.221780.6528
-298.38-0.60741.5515
-1.66151.7472
-3.0181.6111.963
-1.4698
Stdev16.360.095930.088282.0060.003 1550.0034260.071271.3720.23030.073620.20661.1891.1260.37860.5606
0.63850.0011400.055310.038370.27710.99770.049940.00023050.0066510.097490.127561.700.31920.70610.71060.82451.7141.1281.0930.9479
t-ratio-4.10-6.87-4.806.60
-3.884.823.945.522.674.621.66
-3.49-4.62-2.653.841.50
-5.682.213.02
-4.734.172.67
-1.32-1.912.275.12
-4.84-1.902.20
-2.342.12-1.76
1.431.80
-1.55
II,,
0.0000.000Ill.
• its1.0.009• SAil0.099• II.0.0000.009
0.000• •4,• (4:
0.025• I•l0.000•.4i• iS0.0210.036
it,• lIrli•Ip
s = 2.978R-sq = 75.4%Analysis of Variance
SOURCEDFRegression34Error115Total149
R-sq(adj) = 68.2%
SS
MSFp3133.184
92.15210.39
0.0001020.2 18
8.871
4153.401Figure 14
35
I twie u:liuna-up of Regression Model
1. Correction factors onlyThe regression equation isWtChange = 2.35 - 0.505 Gest> 13 - 0.244 GainWt4
2. Correction factors and activitesThe regression equation isWtChange = - 69.5 - 0.514 Gest>13 - 0.231 GainWt4 + i 1.6 LogSleep
- 0.0104 Sip-Stnd + 0.00796 Sip-Walk
R2 = 17.2%
R 2 = 28.6%3.Correction factors, activities, anthropomorphic variables
The regression equation isWtChange = - 87.5 - 0.473 Gest> 13 - 0.437 GainWt4 + 11.4 LogSleep
- 0.0111 Sip-Stnd + 0.0102 Sip-Walk + 0.543 SES.mum + 0.371 BMIJ4mo+ 4.01 BSF/CoSF + 0.271 No.Pregs + 0.143 Age R2 = 44.2%
4. Correction factors, activities, anthropomorphic, medical and child-related factorsThe regression equation isWtChange -99.9-0.473 Gest>l3 - 0.448 GainWt4 + 12.6 LogSleep
- 0.00804 Sip-Stnd + 0.00978 Sip-Walk + 0.649 SES.mum+ 0.348 BMJI4mo + 4.66 BSF/CoSF + 0.3 10 No.Pregs + 0.246 Age-3.68 Smoke? -3.86 Toxhosp - 0.931 BroknSlp + 1.12 BabyWalk+ 1.58 Bottlefd
5. All significant variables including nutrientsThe regression equation isWtChange = - 107- 0.553 Gest>13 - 0.357 GainWt4 + 13.6 LogSleep
- 0.00890 Sip-Stnd + 0.0123 Sip-Walk+ 0.708 SES.mum+ 0.291 BML'4mo + 4.99 BSF/CoSF + 0.548 No.Pregs + 0.251 Age- 4.09 Smoke? - 4.25 Toxhosp - 1.05 BroknSlp + 1.66 Baby Walk+ 1.45 Bottlefd - 1.09 Alcohol + 0.115 AlcBefor -0.000526 Energy+ 2.55 Vit.B6 + 0.0805 Fructose -0.000594 B-Carot
R2=54.3%
Full basic model R2 =64.8%6.Extended model with extra explanatory variables:
The regression equation isWtChange = - 67.1 - 0.660 Gest>13 - 0.424 GainWt4 + 13.2 LogSleep
- 0.0122 Slp-Stnd + 0.0165 SIp-Walk + 0344 SES.mum + 0.281 BMIJ4mo+ 7.58 BSF/CoSF + 0.615 No.Pregs + 0.340 Age - 4.15 Smoke?-5.20 Toxhosp - 1.00 BroknSlp + 2.15 BabyWalk + 0.956 Bottlefd- 0.00647 Energy + 0.122 SFA + 0.116 AlcBefor - 1.31 Alcohol+ 4.16 Vit.B6 + 0.134 Fructose -0.000305 B-Carot - 0.0127 Tot.fol+ 0.222 MUFA + 0.653 Protein - 298 ProtlNrg - 0.607 Zinc+ 1.55 PtTmWork - 1.66 GyneOp + 1.75 Asthma - 3.02 Pain/ab + 1.61 Bleeding+ 1.96 UTrctlnf- 1.47 Anaemia
Extended Model: R 2 = 75.4%
36 0
Table 21:Table of Estimated Effects, Confidence Intervals an" F- '.'alues: Basic Model
Variable Contribution *Estimated WeightConfidence IntervalP-valueto VariationChange (kg) per
(%)Variable UnitLower Bound Upper Bound(Regression coefficient)
Gest . 13 (weeks) 8.3 -0.57-0.78-0.360.0000GainWt4 (kg) 4.1 -0.37-0.56-0.180.0002Correction factors 20.0LogSleep (log minutes) 9.5 12.98.5217.120.0000SIp-Walk (minutes) 2.7 0.0120.0040.0190.0021Slp-Stnd (minutes) 1.7 -0.0085-0.015-0.0020.0142Activity combined 11.9BMIJ4rno (kg/m 2 ) 3.9 0.290.140.450.0003BSF/CoSF 3.0 4.601.837.360.0013Anthropometric 7.6Age (years) 2.6 0.250.090.410.0029No.Pregs 1.4 0.520.050.990.0290Age-related combined 5.6SES 5.0 0.750.401.100.0000Toxhosp(n=0/y=1) 3.5 -4.37-6.80-1.940.0005Smoke? (n=0/y=1) 2.8 -4.08-6.65-1.520.0020Medical and social 10.2BabyWalk(n=0/y=1) 2.0 1.600.432.760.0076BroknSlp 2.0 -1.10-1.91-0.290.0081Bottlefd(n=0/y=1) 1.2 1.440.062.820.0404Associated with infant 5.2.Alcohol (g) 3.1 -1.02-1.62-0.420.0010AlcBefor (mg/lOOml) 1.8 0.100.020.190.0131Alcohol combined 3.8Vit.B6 (mg)
3.9
3.0 1.44.60.0003Energy (kJ)
2.7 -0.0013-0.002-0.00050.0024Fructose (g) 1.5
0.120.020.220.0196
B-Carot (jig)
1.5 -0.0006-0.0011-0.00010.0199SFA (g) 1.5
0.130.020.250.0237
Nutrients combined 6.6Total Explained R' = 64.8 % Unexplained35.2%By Model (Error)
* The contribution quoted is the amount by which the R 2 (the percentage of variation explained by the model)changes if that variable or group of variables is deleted from the final model. Note that since the explanatoryvariables are correlated, the sum of individual contributions may add up to more or less than the combinedeffect of deleting a whole group. The same comment applies to the next table.
37
Table 22:Table of Estimated Effects, Confidence intervals and P- values: Extended Model
VariableContribution*Estimated WeightConfidence Interval:P-valueto variationChange (kg) per(%) Variable Unit
-__-____Jression coefficient) Lower Bound Upper Bound
GainWt4 4.9 -0.42 -0.60-0.250.000()
Correction 23.3factorsLogSleep 9.3 13.2 9.3 17.20.0000Sip-Walk 5.0 0.016 0.0100.0230.0000Slp-Stnd 3.2 -0.012 -0.018-0.0060.0002Activities 13.6BSF/CoSF 6.5 7.6 4.9 10.30.0000BMI/4mo 3.3 0.28 0.140.420.0001Anthropo,nerric 10.7Age 4.6 0.34 0.190.490.0000No.Pregs 1.5 0.62 0.16 1.070.0087Age-related 8.1PtTmWork 1.0 1.6 0.2 3.00.0300SES.mum 0.6 0.34 -0.070.750.0990Work-related 4.2Toxhosp 4.6 -5.2 -7.4 -3.00.0000Smoke? 2.6 -4.2 -6.5 -1.80.0007GyneOp 1.2 -1.7 -3.1 -0.30.0211Asthma 1.0 1.8 0.1 3.40.0362UTrctJnf 0.7 2.0 -0.2 4.10.0751Pain/al, 0.7 -3.0 -6.4 0.40.0809Anaemia 0.5 -1.5 -3.4 0.40.1237Bleeding 0.4 1.6 -0.6 3.80.1559Total Medical 10.5BabyWalk 3.2 2.2 1.0 3.30.0002BroknSlp 1.5 -1.00 -1.75-0.250.0092Bottlefd 0.5 0.96 -0.31 2.220.1369Infant-related 4.9Alcohol 4.8 -1.31 -1.86-0.760.0000AlcBefor 2.0 0.12 0.040.190.0031Alcohol combined 5.5Energy 6.9 -0.006-0.009-0.004 0.0000Protein 5.6 0.65 0.400.910.0000ProtlNrg 5.0 -300 -420-180 0.0000Vit.136 3.7 4.2 2.1 6.10.0001Fructose 1.5 0.13 0.040.230.0086MUFA 1.1 0.22 0.030.4150.0248SPA 1.0 0.12 0.01 0.230.0294Tot.Fol 0.8 -0.013-0.0260.0000.0590Zinc 0.8 -0.60 -1.240.030.0595B-Carot 0.4 -0.000-0.0010.0000.1882
All nutrients 11.7Total Explained R2 75.4% Unexplained24.6%BvModel
IF38
8.3 DISCUSSION OF RESULTS
8.31 The Basic Regression ModelThe basic regression model accounted for 64.8% and the extended model 76.3%of the total variance in weight change from month 4 of pregnancy to month 6 afterbirth. It is surprising that so much of the weight change after pregnancy can beexplained by variables measured during pregnancy. Presumably this means thatthe diet, activity and lifestyle patterns measured during pregnancy are maintainedafter birth.
The significant variables in both regressions will be discussed separately or in likegroups.
(i) Weight gained in the first trimester of pregnancy; Gain Wt4(see Figure 12)To reiterate, if the mother lost weight in the first trimester of pregnancy,this did not seem to affect later weight change. However, if the mothergained weight; every 1 kilogram of weight gained in the first trimestercorresponded to a loss of 0.37 kg after birth (95% CI, -0.55 to 0.18 kg).This could be interpreted as meaning that if the mothers put on weight inthe first trimester they could only expect to lose 20 to 50 percent of thatweight after birth. This was an important variable and accounted for 3.8%of the total variance. Together with gestational age in weeks 20% of thetotal variance was accounted for.
(ii) Activity levels; LogSieep, Sip-Stnd, Sip-Walk (see Figure 15)Activity levels proved to be much more important than diet in determiningthe weight loss after pregnancy, and 11.9% of the total variance in weightchange was accounted for by activity.
The time spent sleeping and lying down was very highly significant in itsown right, however log of the time spent sleeping and lying (log Sleep)fitted the data better and hence the latter variable was used in theregression models. In terms of time itself (rather than log time) everyextra hour per day spent sleeping and lying added an additional 1.03 kg(95% CI, +0.66 - +1.39 kg) of weight after birth. This effect was seen inwomen having up to 12 hours or 720 minutes of sleep, after which itceased. This effect is shown clearly in Figure 15.
The effect of sitting, standing, walking, housework and other moderateactivities was considered in terms of cumulative variables. For exampleSlp-Stnd was time spent sleeping, lying, sitting and standing and Sip-Walkwas time spent on sleeping, lying, sitting, standing, walking, houseworkand other moderate activities. These cumulative variables were necessaryto discern whether a short time spent sitting and standing corresponded toa lot of time sleeping and lying, or a lot of time doing heavy exercise.
39
The Sip-Walk variable is better interpreted as a contrast; that is 24 hoursminus Sip-Walk time equates to time spent on high energy activities, e.g.sport. This variable corresponds to an average weight loss of 0.7 kg. Onehour per day of this high energy activity by the mothers corresponds to anaverage weight loss of 0.7 kg (95% CI, -0.26 to -1 .13 kg).
Exercise levels are something women have some control over. Themessage is clear. Exercise is vital if women wish to lose the weight gainedduring pregnancy.
Mothers' Weight Change (Second Trimester to 6 Months PP)Versus Amount of Time Sleeping/Lying Down
Fitted Values = Log( Time Sleeping/Lying Down)00
00000
-15 *
ccq)::::
I I
500 600 700 800 900 1000 1100 1200 1300 1400
Time Sleeping/Lying Down (minutes)o=Data .=Fitted Values (R2=10.9%) _=Smoothed Average
Figure 15
(iii) Socio-Economic Status, SES-Mum (see Figure 16)This variable is based on the I to 6 Elley-Irving Scale 39,40 developed forNew Zealanders with I indicating the occupations of highest socio-economic status. Those women not working during pregnancy werecoded as zero. Women working in lower socio-economic groupoccupations gained significantly more weight over the focus period thanwomen working in occupations with a higher classification. For example,women in Class 5 gained on average 3.75kg, whilst women in Class Igained on average 0.75 kg (95% CI, +0.4 to +1.1). In all this variableaccounted for 5.0 % of the total variance in weight change.
IIIIII
15
C)
co0-c.2 -5ci)
40
Mothers' Weight Change (Pre-Pregnancy to 6 Months PP)Versus Socio-Economjc Status
(For Those Mothers Employed At 4th Month)25
200)-15
10C
5r
0) -5
-10
-15
-20
12345.6
SES
Figure 16
(iv) Anthropometric Variables Including Number of Pregnancies,BMI14mo, BSF/CoSF, No. Pregs, AgeAnthropometric variables including number of pregnancies accounted for10% of the weight change over the focus period. The higher the BMI andbiceps to costal skinfold ratio, the older the woman, and the greater thenumber of pregnancies she had had, the greater the weight gain postpregnancy.
Body mass index at 4 months, BMlJ4mo, was the most significant variablein this group. Weight gain was on average 0.29 kg higher for each unitincrease in BMI (95% CI, +0.14 to +0.45). That is over the focus periodwomen with a BMI of 24 would expect to gain 0.29 kg more than womenwith a BMI of 23 at 4 months.
Of all the skinfolds measured, by far the most significant in all analysis(birthweight, weight at one year, maternal weight change) has been thebiceps to costal ratio. The costal skinfold as percentage of total skinfoldsdeclined from month 4 of pregnancy to month 12 post partum. Whilst thebiceps skinfold expressed as a percentage of total skinfolds increased tomonth 7 of pregnancy and declined slowly till month 6 post partum andmore rapidly thereafter (see Figure 7). When regressed as individualskinfolds, the skinfold coefficients were of opposite sign. Hence the bestmethod of expressing this contrast in the regression analysis was to use thebiceps to costal skinfold ratio, B SF/Co SF.
141
0) -0.2
0) -1.CTJ
o -2.2
0)
G)-3.2
.c0
-5.2
Weight gain with increasing number of pregna-cies is an often observedphenomenon. For each additional previous pregnancy the women in thisstudy gained an extra 0.5 kg on average over the period. Over and abovethe effect of previous pregnancies, the women also gained on average of0.25kg for every year of increasing age (95% CI, +0.09 to +0.41 kg/year).
(v)Smoking, Smoke? (see Figure 17)This was a yes (=]), no (=0) indicator for women who smoked duringpregnancy. There were only 12 women who smoked and these lost onaverage 4.08 kg during the period (95% CI, -6.51 kg to -1.66 kg). Thisreflects the well known effect of tobacco as an appetite suppressant.
Mean Weight Change vs Whether She Smokes
No YesDoes the Woman Smoke?
Figure 17
(vi) Hosp italised for Toxaemia, Tox hosp. (see Figure 18)Again this was a yes (=1), no (=0) indicator. There were 11 womenhospitalised for toxaemia and these women lost on average 4.37 kg morethan those who did not have toxaemia (95% CI, -6.8 kg to -1.9 kg). Thisis an interesting association and deserves further study.
42
Mean Weight Change v Hospitalised For Toxaemia
C)
a)C) _____Co -1.5C)
-2.5 —CD
-3.5-
No YesWas She Hospitalised For Toxaemia?
Figure 18
(vii) Variables Associated with the infant; broken sleep, Brokn Sip; babywalking at 12 months, Baby-Walk; bottle feeding at month 2 postpartum, Bottlefd (see Figures 19 to 21).Together these variables accounted for 5.2% of the total variance inweight change from month 4 of pregnancy to month 6 post partum.Broken sleep, BroknSlp, was coded as I if the woman was woken at least3 times a night, 2 if woken twice, and 3 if woken at most once a night.The women who had the least broken sleep were estimated to lose 2.2 kgmore than women who had the most broken sleep (95% CI, -1.91 to -0.29). We have taken this to mean that these more highly stressed women,obtaining less sleep, were eating more, and/or exercising less. This effectis shown clearly in Figure 19.
Mean Weight Change v Frequency of Broken Sleep
2.5-0)C) I1.5-0
0.5 -C) I--0.5 -a) I
>=3 Times2 Times<=1 TimeHow Many Times Sleep Broken Per Night
Figure 19
43
0.2
ca
a)0)
0
0) -0.8
LD
a)
Q)
0-1.8
It may seem a little odd to include the variable baby walking at 12 months(1yes, O=no), in a model for weight change to 6 months post partum.However we have taken this as an indicator of motor development in theinfant and hence how active the child is. Again we feel this suggestsmaternal stress with women having a baby walking at 12 months increasingtheir weight by 1.6 kg on average over the focus period; (CI 95 1/o CI, +4.3kg to +2.7 kg). This is illustrated in Figure 20.
Mean Weight Change v Baby Walked By 12 Months?
No Yes
Was The Baby Walking By 12 Months?
Figure 20
There were 134 woman who exclusively breast fed at month 2 postpartum, 10 who exclusively bottle fed and 33 who practisedcomplementary feeding. In the regression the bottle fed group includesthose who complemented. Those who bottle fed gained 1.4 kg more in theperiod, than those who exclusively breastfed (95% CI, +0.07 kg to +2.82kg). (See Figure 21). It is worth noting that those who usedcomplementary feeding had the highest weight gain of the three groups. Inaddition bottle feeding was more common among beneficiaries and thosein the lower socio-economic groups.
44
0)-xC)0)CCo
-C0)C)
U)0)-c0
Mean Weight Change v Whether Bottle Was Used
No YesWas The Bottle Being Used At 2 Months?
Figure 21
(viii) Alcohol intake, alcohol, AlcBefor (see Figure 22).Alcohol being a toxin was not included with the nutrient group in thisdiscussion. Alcohol intake before pregnancy, AlcBefor, calculated as theblood alcohol level in mg alcohol/lOOmI blood resulting from the mothers'stated usual alcohol consumption, and alcohol intake during pregnancy43.Alcohol, calculated in grams from the weighed diet records were bothfound to be significant variables in this and the birthweight analysis.
For those women who drank during pregnancy, on average every gram ofalcohol (equivalent to -30m1 of beer) consumed per day resulted in theloss of 1 kg of body weight over the period (95% CI, -1.6 to -0.4). Asdietary alcohol intake during pregnancy had a significant negative impacton birthweight, perhaps this loss of weight in the period to 6 months afterbirth reflected the accumulation of less maternal and foetal tissue duringpregnancy.
In contrast alcohol consumption before pregnancy (and presumably after)increased body weight on average by 0.1 kg for every I mg/100 mlincrease in blood alcohol level (ie - 0. 1 kg for every 12 to 15 ml increasein beer consumed (95% CI, ±0.02 to 0.18). Most of these womenconsumed alcohol at least once a week. Together alcohol accounted for3.8% of the total variance in weight change.
45
UUUciEJUEl
Figure 22 [1(ix) Nutrient Intake; Vitamin B6, Vit.B6; Energy; Fructose; 13-Carotene, - [1
Carot; SFA, Saturated Fatty AcidsIn all, nutrient intake accounted for 6.6% of the total variance in weightchange, or 10.5% of the total variance if alcohol intake was also included.
Only 4 nutrients, and energy intake were significantly related to weightchange. Energy intake was negatively related to weight gain (some of ourbiggest eaters were very active), but the effect was not strong in itself (seeFigure 23). Its importance in the regression depended on its relationshipUwith Vitamin B 6, saturated fatty acid, fructose and alcohol intake. Ingeneral high energy intakes also meant high intakes of these nutrients.This is illustrated in the plots of energy vs SFA, fructose and Vitamin B6intake in Figure 24 to 26.
ciUUciEl
I46 U
Mothers' Weight Change (Second Trimester to 6 Months PP)Versus Average Daily Energy Intake
15 —00
00 0 0
-
000 0 0 00ci)- c)
0 oo0
.)-5ci) 000% 00 0 -
0 00 00 0000
0
000
-15 -
5000 10000 15000Energy (kJ)
o=Data .=Fitted Line =Smoothed
Figure 23
Daily Energy Intake versus Saturated Fatty Acids
0
0
ci0 (-
15000 - -
-D
ci)cci
0)I-a)w(cio
5000 - 0—r
20
o=Data _=Smoothed A
0
i
0(^)8
Obb
Cli
0 0@
00- 0, ^0
000
304050
[ioLi]
SEA (grams)e (lowess curve)
0
0
Figure 24
47
15000
—)
C)
Co
>.. 100000)
C)
LU>CC
C)5000
UIJ1jUUUUci
Figure 25 ciUUUUciciUFigure 26
UOn average for each additional gram of fructose in the diet/day the womenput on 0.12 kg of weight over the regression period, and for eachadditional gram/day of saturated fatty acid the women put on 0.13 kg ofwei ght over the regression period (95% CI, +0.02 to +0.2 kg for fructose;+0.02 to +0.25 for SFA). The effect of these variables was potentiallyU
148
15000
CD 10000
5000 10
o=Data
considerable as the mean fructose intake was 22 g, range 4g to 53g, andthe mean SFA intake was 49g, range 39g to 58g. While it is fashionable atthe moment to often ascribe fat accumulation to fat intake alone, in thisstudy carbohydrate intake is shown to be potentially more important.Fructose intake is of course only a marker for certain dietary patterns.Study of the women's individual 16 day weighed diet records showed thatwomen with high fructose intakes also had high energy intakes and weredrinking large amounts of fruit juice (200 to 1300 ml/day), carbonatedbeverages (200 - 600 ml/day) as well as eating 3 to 4 serves of fruit/day,and 6 to 8 meat pies/16 day period and in some instances large amounts offruitcake. Women with low fructose intakes drank very little fruitjuice orcarbonated drinks, ate less than 1 serve of fruit a day and had a low intakeof meat pies and fruitcake. High fruitjuice consumption as an importantcontributor to weight gain should be more widely publicised. The publicperception is that fruitjuice is a healthy food.
As one would expect, when the 16 day weighed diet records wereexamined, women with high saturated fatty acid intakes also had highenergy intakes, most ate meat daily with fatty products being consumedfrequently (sausages, mince pies, sausage rolls, KFC, battered fish,hamburgers, chops and mince). These subjects also ate moderate to largeamounts of dairy products (butter, cheese) and had takeaways at least 4 to6 times in 16 days. Many also consumed large amounts of cakes andbiscuits (50 to 120g), 10 to 12 times/16 days. The opposite pattern wasseen in women with low saturated fatty acid intakes.
The importance of Vitamin B 6 in the regression was a surprise. MeanVitamin B6 intake in this study ranged from 0.6 to 3.6mg, mean 1.6mg.For every 1mg increase in intake the women gained on average 3.0kg inweight over the regression time period (95% CI, +1.4 to +4.6 kg). Dietshigh in Vitamin B 6 were high energy, most included 12 to 16 servings ofmeat and 10 to 12 servings of cereals high in B 6 over the 16 day recordperiod. These women also had high intakes of fruit and vegetables; 5 to 6servings/day on average, and most ate bananas daily, the latter being highin B6 . Those with a low B 6 intake had a low energy intake, consumedsmall serves of meat, often no breakfast cereal and a maximum of 1-2serves of fruit and vegetables a day. The women with high B 6 levels wereeating well nutritionally speaking. Perhaps for this group lower activitylevels were the major reason for weight gain.
In the regression the coefficient for 3-carotene was negative. Mean 13 -carotene intake was I 105 jig, range 862 to 9238jig. For every jig increasein 13-carotene intake women lost 0.0005 kg (95% CI, -0.01 to -0.0001kg).This is not a large effect. The difference in weight loss between the upperand lower quartile of intake is estimated at —1 .0kg. High 13-carotene dietswere also high in energy and dietar y fibre. For example these womenconsumed 6 to 7 serves of vegetables per da y and between 21 to 36g offibre. Low carotene diets included onl y 6w 21 g of fibre and 1 (02 serves01 fruit and vegetables per day.
'9
13-carotene would seem to be a marker for diets high in certain types offibre from fruit and vegetables which aid weight loss. This subjectdeserves further study.
8.32 The Extended Regression Model.The extended regression model accounted for 76.3% of the total variance inweight change between month 4 of pregnancy and month 6 post partum. In thismodel more nutrients were implicated in weight change. Mono unsaturated fattyacid, MUFA and protein intake was associated with weight gain and total folateTot.fol, zinc intake, and the percentage of total energy from protein, ProtlNrgwere associated with weight loss. In all regressions the percentage of total energyfrom fat, protein carbohydrate and alcohol have been considered as possiblesignificant variables. This is the first time one of these has proved to besignificant, and it is not the percentage of energy from fat that one would expect.
Women with asthma, bleeding during pregnancy (bleeding), urinary tractinfections during pregnancy (UTrctlnf), tended to gain weight over the period.Whereas women who had had previous gynaeological operations, abdominal painand anaemia during pregnancy lost weight.
Some of these factors deserve further study. However time does not permit moredetailed investigation for this report.
i/i INFAP.[f ME4SIJRBIEArTS FROM BIRTH 10 ONE VE4R
9.1 METHODS OF ANALYSISThe measurements in this analysis were taken from birth records, plunket or doctor'srecords at 7 weeks and measurements by the data collectors at 1 year. Standard statisticaltechniques were used in the analysis.
9.2 RESULTSThe mean (standard deviation) of infant's weight, length and head circumference at birth,6 weeks and 1 year are given for all infants as well as boys and girls separately in Table23. Length measurements at birth were only available for a few infants so were notincluded in the table. Histograms showing the distribution of babies weight and headcircumference at birth and 12 months are shown in Figures 27 to 30. In additionhistograms showing the distribution of infants length, and weight for length are given inFigures 31 and 32.
II
50
Table 23:Infant Anthropometric Measurements
Mean (SD)NumberWeightLengthHead Circumference (cm)
(cm)Birth:All infants1963561(596) 35.3(1.6)
Girls only843498(525) 35.0(1.3)
Boys only1083631(626) 35.6(1.7)
6 weeks:All infants1754898(665)57.5(3.5)39.0(3.0)
Girls only754778(599)56.7(2.5)38.8(2.5)
Boys only974994(687)58.0(4.0)39.1(1.3)
1 year:All infants1409928(1291)75.5(3.5)47.2(1.6)
Girls only569484(1182)74.0(3.0)46.6(1.9)
Boys only8210,280(1 199)76.5(3.5)47.6(1.3)
Weight of Baby at Birth
70
60
>• 500
40
C- 30U-
20
10
0
1800 2300 2800 3300 3800 4300 4800 5300
Weight of Baby (grams)
Figure 27
51
50
40
>030G)
20U-
10
0
Babies' Head Circumference at Birth
31 32 33 34 35 36 37 38 39 40 41
Head Circumference (cms)
Figure 28
Weight of Baby at Twelve Months
50
40
30
0w 20U-
10
0
one year
6000 7000 8000 9000 10000 11000 12000 13000 14000Weight (grams)
Figure 29
52
Babies' Head Circumference at twelve months
60
50
>o 40Ca)a-a)U20
10
0
one year
44464850525456
Head Circumference at 12 months (cms)
Figure 30
Histogram of Babies' growth to twelve months
40
> 300Ca)a- 20a)U-
10
0
one War
100 110 120 130 140 150 160 170
Weight for Height at 12 months
Figure 31
53
Height of Baby at Twelve Months
30
'20Ca)0a)IL 10
[ii
66 68 70 72 74 76 78 80 82 84Height of Baby
Figure 32
9.3 DISCUSSION OF RESULTSTwelve percent more boys than girls were born to the women in the sample. Thebirthweight of the infant ranged from 1814g to 5260g. Usually infants with birthweights<2500g and > 4200g are considered at risk. In this sample 3.6% of babies weighed lessthan 2500g at birth, 11.7% weighed more than 4200g and 6.6% more than 4500g.
Using the Plunket growth charts as a reference 6.4% of infants were below the thirdpercentile for weight, and 11.6% for height at one year. In addition 6.4% were above the97th percentile for weight and 2.3% for height.
Table 24 shows the percentage of girl and boy infants at birth and 1 year below the 3rdpercentile and above the 97th percentile for weight and height according to the NCHSgrowth charts. These are more useful than the Plunket charts as they differentiate for sex.While the percentage of girl and boy babies below the 3rd percentile is around what wewould expect in a normal sample, the percentage of babies above the 97th percentile isnot. Six times as many boy babies and. nine times as many girl babies were in thiscategory than would normally be expected. That is at one year we have more shorterboys and more heavier boys and girls than would normally be expected according to theNCHS charts. Whether these heavier infants present a health risk needs furtherinvestigation.
As was expected, the boys were in general heavier and longer than the girls at allmeasurement dates. The difference in the mean head circumference between the sexeswas much smaller. ie 0.6cm at birth. 0.3cm at 6 weeks and 1cm at I year.
Table 24:Infants in the NCHS 'At Risk' Groups i.e. < 3rd Percentile and > 97thPercentile
Below the 3rd PercentileAbove the 97th Percentile% of Babies % of Babies
AT BIRTHWeight- Boys 3.7 17.8
- Girls 2.4 27.4
ATONE YEARWeight- Boys 3.7 6.1
- Girls 0 5.4
Height- Boys 5.3 6.6-Girls 3.8 1.9
10. INFLUENCES OAf BABIES' BIRTHWEIGIIT
10.1 METHODS OFANALYSISThe standard statistical techniques and methods of regression analysis already referred toin 6.1 are used again to assess this data.
10.2 RESULTSThere were 196 babies for whom complete data sets were available at birth. The meanbirthweight for the babies in the sample was 3561g range 1814 to 5260g. Details ofbabies birth measurements considered as a group and broken down by sex are presentedin 9.2 and 9.3. (See Tables 23 and 24, Figures 27 to 32).
The basic regression model is shown in Figure 33. This model is restricted to the veryhighly significant variables. An extended model which includes some less significantvariables is provided in Figure 34. We are less confident of this model but it providessome useful indicators for further research. The build-up of both regression models isshown in Table 25. In addition Tables 26 and 27 give the percentage of total variance inbirthweight explained by each of the variables in each of the models, their 95% confidenceintervals and p values. Selected lowess curves, interval and box plots are providedthroughout 10.2 to illustrate the effect of some of these variables on birthweight.
55
Table 25:Build up of the Regression Analysis: Babies' Birth weight.
The regression equation isWEIGHT= 3031 + 22.6 DaysLae + 29.4 BMI -254 BSFICoSF R2 = 22.0%
The regression equation isWEIGHT = 3504 ± 20.2 DaysLate + 30.7 BMI - 256 BSF/CoSF - 1.01 SleepLie
+ 183 PreSchCh - 278 Smoking + 220 Cramps R2 = 34.8%
The regression equation isWEIGHT = 3841 + 22.1 DaysLate + 33.8 BMI -456 BSF/CoSF - 1.29 SleepLie
+ 187 PreSchCh -307 Smoking + 284 Cramps -0.115 Manganes+ 0.0923 Chloride - 1.33 Sulphur + 104 Zinc
Full basic model R2=41.1%
Extended Model
The regression equation isWEIGHT= 3897 + 24.1 DaysLate - 10.8 WhenLate + 23.0 BMI + 52.3 DIFBMI70
-481 BSF/CoSF- 1.40 SleepLie + 142 PreSchCh -38.9 SESb4+ 278 Fathwork + 179 beneonly + 36.7 DRINKERS - 181 Smoking+ 1413 Oedtox? - 523 Oedtox - 431 LegVeins + 372 Cramps+ 399 Bleeding - 2.79 Sulphur + 103 Zinc - 63.2 VitmnBl2+ 2.21 Tot.Fol + 31.7 Monofat - 0.164 Manganes + 1.80 VitaminC+ 65.3 Maltose - 16.0 DietFihr + 391 Copper + 0.0928 Chloride- 12.8 Glucose + 1.02 Cholestl + 0.369 Calcium - 8.16 SatFat
Extended model R 2 = 60.3%
Regression Analysis For Basic Birth weight Model
The regression equation isWEIGHT = 3841 + 22.1 DaysLate + 33.8 BMI + 187 PreSchCh - 307 Smoking
- 456 BSF/CoSF - 1.29 SleepLie + 284 Cramps - 1.33 Sulphur+ 104 Zinc - 0.115 Manganes + 0.0923 Chloride
185 cases used 12 cases contain missing values
PredictorConstantDaysLateBMIPreSchChSmokingB S F/C oSFSleepLieCrampsSulphurZincManganesChloride
Coef3841.222.10633.791187.01
-306.63-455.6
-1.2943284.2
-1.3274103.51
-0.115340.09227
Stdev394.73.3569.97050.0280.15167.3
0.3608104.0
0.506038.24
0.033310.03740
T-Ratio9.736.593.393.74
-3.83-2.72-3.592.73
-2.622.71
-3.462.47
P-value0.0000.0000.0010.0000.0000.0070.0000.0070.0090.0070.0010.015
s = 479.6R-sq = 41.1% R-sq(adj) = 37.3%
Analysis of Variance
SOURCEDFSS
MS
FP-valueRegression II 27732766
2521161
10.960.000Error 173 39791436
230008
Total 184 67524200
Figure 33
7
Regression Analysis For Extended Birthweight ModelThe regression equation isWEIGHT 3897 + 24.1 DaysLate - 10.8 WhenLate + 23.0 BMI + 52.3 DIFBMI70- 481 BSF/CoSF
- 1.40 SleepLie + 142 PreSchCh - 38.9 SESb4 + 278 Fathwork + 179 beneonly+ 36.7 DRINKERS - 181 Smoking + 1413 Oedtox? - 523 Oedtox -431 LegVeins + 372 Cramps
+ 399 Bleeding - 2.79 Sulphur + 103 Zinc - 63.2 VitmnB 12 + 2.21 Tot.Fol + 31.7 Monofat- 0.164 Manganes + 1.80 VitaminC ± 65.3 Maltose - 16.0 DietFibr + 391 Copper+ 0.0928 Chloride - 12.8 Glucose + 1.02 Cholestl + 0.369 Calcium - 8.16 SatFat
PredictorCoefConstant3897.50DaysLate24.11WhenLate-10.85BMI22.98DIFBMI7052.28BSF/CoSF-481.30SleepLie-1.40PreSchCh141.98SESb4-38.88Fathwork278.30beneonly179.00DRINKERS 36.67Smoking-181.22Oedtox?1413.00Oedtox-523.30Leg Veins-431.20Cramps372.20Bleeding399.40Sulphur-2.79Zinc102.52VitmnBl2-63.25Tot.Fol2.21Monofat31.71Mangaries-0.16VitarnjnC1.80Maltose65.32DietFibr-15.96Copper390.90Chloride0.09Glucose-12.83Cholestl1.02Calcium0.37SatFat-8.16s = 420.6R-sq = 60.3%
Stdevt-ratiop447.6008.710.0005.5534.34
0.000
11.390-0.95
0.3439.6442.380.01919.1102.740.007168.000-2.86
0.005
0.363-3.87
0.00056.8302.50
0.014
18.310-2.12
0.035120.7002.31
0.023
199.7000.90
0.37234.2701.070.28686.650-2.09
0.038
366.1003.86
0.000162.600-3.22
0.002
193.300-2.23
0.027100.6003.700.000159.3002.510.0130.641-4.36
0.000
39.0702.620.01023.410-2.700.0080.8782.510.01313.3902.370.0190.043-3.80
0.000
1.0611.70
0.09241.8801.56
0.121
12.750-1.25
0.213280.7001.39
0.166
0.0382.420.017
6.374-2.010.046
0.7731.320.190
0.1901.940.054
7.052-1.16
0.249R-sq(adj) = 51 .0%
Analysis of VarianceSOURCE DFSSRegression32 36749124Error137 24240396Total169 60989520
MSF p
11484106.49 0.000176937
Figure 34
580
Table 26:Table of Estimated Effects, Confidence Intervals and P-values: Basic Model.
VariableContribution toEstimated ChangeConfidenceintervalP-valuevariation (%)to Babies Weight
(g per variable unit)Lower BoundUpper BoundDaysLate 14.8 22.1 15.5 28.70.000BMI 3.9 33.8 14.1 53.50.001BSF/CoSF 2.5 -456 -786 -1250.007
Physical Variables 23.6
Smoking 5.0 -300 -470 -1500.000PreSchool Children 4.8 187 88 2860.000SleepLie 4.4 -1.3 -2.0 -0.60.000Cramps 2.5 280 80 4900.007
Social and Medical 15.4
Manganese 4.1 -0.12 -0.18 -0.050.001Zinc 2.5 104 28 1790.007Sulphur 2.4 -1.3 -2.3 -0.30.009Chloride 2.1 0.09 0.02 0.170.015
Nutrients 6.3Total Explained by Unexplainedthe Model R2 = 41.1% (Error) 58.9%
* The contribution quoted is the amount by which the R-squared (the percentage explained by the model)changes if that variable or group of variables is deleted from the final model. Note that since the explanatoryvariables are correlated, the sum of individual contributions may add up to more or less than the combinedeffect of deleting a whole group. The same comment applies to the next table.
59
Table 27:Table of Estimated Effects, Confidence Intervals and P- values:Extended Model.
Variable Contribution toEstimated Change toConfidence IntervalP-valuevariation (%) Babies Weight(g per variable unit) Lower Bound Upper Bound
DaysLate 5.5 24.1 13.1 35.10.0000WhenLate 0.3 -10.9 -33.4 11.70.3426BMI 1.6 23.0 3.9 42.10.0185DIFBMI70 2.2 52.3 14.5 90.10.0070BSF/CoSF 2.4 -480 -810-1500.0048SleepLie 4.3 -1.4 -2.1 -0.70.0002Ph ysical Variables 20.9PreSchCh 1.8 142 30 2500.0137SES1>4 1.3 -39 -75 -30.0354Fathwork 1.5 280 40 5200.0226beneonly 0.2 180 -210 5700.3717DRINKERS 0.3 37 -31 1040.2864Smoking 1.3 -180 -350 -100.0383Oedtox? 4.3 1410 69021400.0002Oedtox 3.0 -520 -840 -2000.0016LegVeins 1.4 -430 -810 -500.0273Cramps 4.0 370 170 5700.0003Bleeding 1.8 400 80 7100.0133Social and Medical 17.1
factorsSulphur 5.5 -2.8 -4.1 -1.50.0000Zinc 2.0 103 25 1800.0096VitmnBl2 2.1 -63 -110 -170.0077Tot.FoI 1.8 2.2 0.5 4.00.0131Monofat 1.6 31.7 5.2 58.20.0193Manganes 4.2 -0.16-0.25-0.080.0002VjtamjnC 0.8 1.8 -0.3 3.90.0915Maltose 0.7 65 -17 1480.1211DietFibr 0.5 -16.0-41.1 9.30.2128Copper 0.6 390 -160 9500.1660Chloride 1.7 0.09 0.02 0.170.0169Glucose 1.2 -12.8 -25.4 -0.20.0461Cholestl 0.5 1.0 -0.5 2.50.1902Calcium LI 0.37 -0.01 0.740.0542SatFat 0.4 -8.2-22.15.80.2489Nutrients 12.6
Total Explained byR2 = 60.3 % Unexplained39.7%the Model (Error)
10.3 DISCUSSION OF RESULTS
10.31 The Basic Regression ModelThe basic regression model accounted for 41.1% of the total variance in babiesbirthweight and the expanded model for 60.3%. The significant variables in thebasic regression model will be discussed separately or in like groups.
Gestational Age at Birth, Davslate (See Figure 35).On average babies were horn half a day late, median 2 days Iae. ran ge 40days early to 26 days late. The increase in foetal weight \viih increanLr
i.
60 -
gestational age is clearly shown in Figure 35. On average babies weightincreased by 22.1 g for every day late (95% Cl, +15.5 to +29g).
Weight of Baby vrs no of days late
003
4003CU
Z 3000
2000
'-'0'
L
cko'' 00)0
I I I
-40-30-20-10010no of days late
IN
2030
Figure 35
ii.Prepregnancy Body Mass Index, BMI (See Figure 36).Body Mass Index is a measure of bulk and is accepted as a very usefulindicator of pregnancy outcome. Recommended weight gain duringpregnancy is now tied to actual prepregnancy BMI. In this study asmother's prepregnancy BMI increased so in general did baby'sbirthweight. Body mass index in our sample ranged from 17.1 to 40.3,mean 23.3. For every unit increase in BMI, baby's birthweight increasedon average by 34g (95% Cl, +14 to +53g).
Weight of Baby vrs body mass index
1000
4000.0
.0Co
o 3000C)
2000
o=actual .-=fi
of9S0 0o
Q0ç
, 0
20 30 40
body mass index
Figure 36
61
U)EU)0)C
>.'.0U).0
0
-c0)ci)
Ratio of Biceps to Costal Ski nfolds at Four Months, BSF/CoSF(See Figure 37).The change in biceps and costal skinfolds during pregnancy is described indetail in Figure 37. The contribution of the costal skinfold to the total sumof skinfolds decreases from the fourth month of pregnancy, whereas thecontribution of the biceps skinfold increases. We chose to use the ratio ofthese skinfolds as this best described their behaviour during pregnancy.The average biceps to costal ratio was 0.7, range 0.2 to 1.4. For every 0.1increase in the ratio, baby's birthweight decreased by -45.5g (95% CI, —78.5 to -l2.5g). So the greater the maternal skinfold ratio the smaller thebaby. Body fat distribution is influenced by sex hormone levels. Thisskinfold ratio could be an indicator of hormonal levels deterimental tofoetal development. This is a new finding and we will be investigating itfurther.
The biceps to costal ratio at fourth months is not only a highly significantinfluence on birthweight, it is also an important indicator of weight gainafter birth. However the greater the skinfold ratio the greater the weightgain. Again this is a new finding and we will be investigating it further.
The anthropometric variables in i, ii, and iii account for 22% of the totalvariance in babies birthweight.
Weight of Baby vrs Ratio of Biceps to Costal Skinfolds
05000
°000000
)7- o
1 n. ,AV
30001)O
& 8 00
200000
02 0.7 12ratio of biceps to costal
Figure 37
62
ivSmoking During Pregnancy, Smoking(See Figure 38)The dramatic retardation of foetal growth due to smoking is clearly shownin Figure 38. Non smokers were coded 0. Women who smoked less thanfive cigarettes a day were coded one, women who smoked less than tencigarettes a day were coded two and women who smoked more than tencigarettes a day were coded three. Basically for every five cigaretteincrease a day babies birthweight dropped by 306g on average (96% CI, -454 to -l47g). Smoking is the single most detrimental lifestyle effect onbirthweight.
Weight of baby vrs total smoking activity
3600-3500-3400-
C
;S 3300-3200-
'53100-3000-
CD2900-2800- :E
0123Total smoking
Figure 38
VTime Spent Sleeping and Lying in the Fourth Month, SleepLie(See Figure 39)On average the women slept or lay down for 621 minutes per day in thefourth month of pregnancy, range 458 to 1373 minutes. The more timethe women spent lying the lower the birthweight of the baby. On averagefor every extra hour spent sleeping and lying the babies birthweightdecreased by 78g (95% CI, -120 to -30g). It has been shown thatprolonged high energy expenditure activity reduces birthweightsignificantly. However this is the first time that an extremely sedentarylifestyle has been shown to impact on birthweight. Perhaps a sluggishcirculation system delivers less oxygen and nutrients to the foetus andhence retards foetal growth. The corollary of this finding is that amoderate level of activity is optimum for foetal well being. We will beinvestigating this finding further.
63
00
39003800
I-370036003500
CO-°340033003200
CD 31003000
Weight of Baby vrs minutes spent sleeping and lying down
i) 5000EcaCD
4000
CU
>.0
.0
o 3000-z0)
2000I I
500 600 700 800 900 1000 1100 1200 1300 1400sleep 11e4 (minutes)
Figure 39
ViPre-School Children, Kids. No.(See Figure 40)The total number of children born to the mother did not impactsignificantly on birthweight, however the number of pre-school childrenthe mother had did. Mothers had up to three pre-school children(median=]). For every successive pregnancy birthweight increased onaverage by 187g (95% CI +88 to +285g). Hence recent previouspregnancies have a positive effect on birthweight.
Weight of Baby vrs no of Pre school children
0123no of pre school children
Figure 40
ViiBraxton Hicks Contractions, Other Cramps, Cramps(See Figure 41)This is a 'mixed bag' variable and as such could be slightly suspect.However it could point the way for further research. Alone it isinsignificant, but in the presence of other variables it becomes significant.It is a Yes=], No=O variable. Women who suffered Braxton Hickscontractions and other 'cramps' had on average babies who were 248gheavier than women who did not (95% CI +79 to +489). There were 28women in this category.
Weight of Baby at Birth vs Total Cramps.
0E3800Co
3700
Co
>nCo
36000
3500
noTotal Cramps
Figure 41
These last three variables v and vi and vii account for a further 12.8% of the totalvariance in birthweight.
ViiiNutrient Intake, Chloride, Sulphur, Zinc, ManganeseTogether the nutrients accounted for 6.3% of the total variance inbirthweight in this model. Only four nutrients were included, most beingunimportant in themselves, but a marker for a dietary pattern that affectedfoetal growth.
Manganese and chloride are closely related and there is some interactionbetween them. They are surprisingly found in high levels in similar foods.Examination of the women's weighed diet records showed that womenwith high manganese and chloride intakes had high energy intakes anddiets high in wholegrain cereals e.g. weetbix, porridge, muesli, bran,wholemeal and wholegrain bread, as well as high tea intakes. Women withlow manganese and chloride had low energy intakes and consumed littlewholegrain cereal in an y form. In contrast to what we expected chlorideintake was not particularly associated with processed food intake.
65
Manganese intakes varied between I 157.Lg and 8788p.g, mean intake4456p.g. For every lag of manganese intake birthweight fell by 0.1 g (95%CI -0. 18 to -0.05), that is for every I 000ig increase in manganese intakebirthweight fell from between 50 to 200g.
Chloride intakes ranged from 2171mg to 10314mg, mean 4968mg.However chloride had a positive impact on birthweight. For every 1mgincrease in chloride intake, birthweight increased by 0.09g on average(95% CI, +0.08 to +0.17g). Of these two however manganese was by farthe most significant variable. Women with high wholegrain cereal intakeswould also have had high phytic acid intakes. The recent work ofProfessor Rosalind Gibson shows the impact of high phytic acid intakes onzinc and iron absorption. The high insoluble fibre content of wholegraincereals would also decrease the absorption of a number of nutrients,including fats. Taken together this decrease in nutrient absorption couldexplain the negative impact of wholegrain intake on foetal growth. Thiseffect was not seen for dietary fibre as a whole but is peculiar towholegrain cereals. In all regression models the negative impact ofmanganese was very highly significant. However I do not think it wouldbe useful to recommend that pregnant women reduce their wholegraincereal intake.
Sulphur was another marker nutrient for a diet high in meat, often in largeserves, often high in eggs (6-18 eggs/16 days) and high in cheese, 50-60gon most days. These were very high animal protein diets. Women withhigh sulphur intakes also had high energy intakes. High sulphur (highanimal protein) diets had a negative impact on growth. Mean sulphurintake was 838mg range 404 to 1494mg. For each 1mg increase insulphur intake birthweight fell between -2.3 and -0.3g, with a best estimateof -1.32g. That is for every 100mg increase in dietary sulphur birthweightfell on average by 1 32g. This indicates that very high animal protein dietsmay not be desirable during pregnancy.
The women's zinc intake ranged from 2.52mg to 24.7mg mean 10.27mg.For every 1mg increase in zinc intake babies weight increased by 103g(95% CI, +28 to 179g). Women with high zinc intakes often had highenergy intakes and ate moderate to large servings of meat and bread andcereals (5-12 serves each day). They also ate 6-9 eggs over the 16 dayperiod. On the other hand women with low zinc intakes generally hadlower energy intakes, were vegetarian or had small serves of meat 10 to 13times in 16 days, low to moderate amounts of cereals (3-6 serves/day) and:!^5 eggs in the 16 day period.
Zinc is the only highly significant nutrient where we can actually say itsimpact on birthweight is due to the level of intake of the nutrient itself. Allthe other highly significant nutrients were markers for a dietary pattern thathad a positive or negative impact on birthweight. It is interesting that zincis the most significant, not iron or folate for example. Zinc is deficient inman y New Zealand soils. The impact of zinc intake on foetal growth inNew Zealand women needs more investigation.
66
Plot of Weight of Baby vs Sulphur
5000U)ECt
4000Ct
0 3000-C0)C)
2000
oC00 O
0 ('C
&
00QCp 'Oc 00O 000
0000 0
500 1000 1500Sulphur
Figure 42
10.32 The Extended ModelThis model has been included to indicate other influences on birthweight thatcould do with further investigation. Only those variables additional to thosealready discussed in the main model will be considered.
Physical VariablesWhenlate is an additional indicator for babies which are born late. It is acorrection term to adjust for a slightly different rate of weight gain beforeand after the expected delivery date.
DIFBMI 70 is the difference between the mother's pre-pregnancy BMIand her BMI at seven months. It gives an indication of the maternal andfoetal tissue increment due to pregnancy. Increasing BMI difference has astrongly positive impact on pregnancy.
Physical variables account for 25.1% of the variance in this model.
iiSocial VariablesSESb4 is mothers socio-economic status prior to pregnancy using 1-6 onthe Elley-Irving Scale 39,40 with seven being the code for benefit.Birthweight declines with decreasing socio-economic status. (See Figure43).
Fathwork is a Yes=], No=0 coded variable for a husband/partner thatworks. Husbands/partners working has a positive impact on birthweight.(See Figure 44).
Beneonly is a Yes=l. No=0 indicator variable for a mother on a benefitwith no other income. This an insignificant variable.
167
3600
CU3500
"63400
.0
3300
3200
DRINKERS is the code name for mother's drinking habits before andduring pregnancy. Again this an insignificant variable.
Social factors account for a further 10.5% of the total variance inbirthweight.
Weight of Baby vrs Socio Economic Status of mother
S 5000E0)
4000.0a).0
230000)a)
2000
* **
Mothers SES
Figure 43
Weight of Baby ws Father Working
0Father Working
Figure 44
I68
iiiMedical ProblemsOedtox? and Oedtox. This pair of variables refers to an interaction effectof oedema and toxaemia on birthweight. The first indicated whether thewoman had oedema and, by itself, was positive. However some of thewomen with oedema also had toxaemia, which was significantly negative.Overall, women with oedema but not toxaemia had babies 747g heavier;women hospitalized for toxaemia had babies 188g heavier; while womenindicated for toxaemia had babies 811 g lighter on average than womanwithout oedema.
LegVeins was a Yes/No variable for women who had problems withvaricose veins during pregnancy. Again it has a negative impact onbirthweight.
Bleeding is self explanatory Yes/No variable. For some reason womenwho had spotting or bleeding during pregnancy produced larger babies.This effect is illustrated in Figure 46.
Medical factors accounted for a further 11.8% of the total variance inbirthweight in this model.
Weight of Baby vs Mother's Oedema and/or Toxaemia
II
1-iNeitherOedema ToemiaToemia
OnlyHospitalised Medicatedmothers oedema and/or toxaemia
Figure 45
4500-z.0
.0cc 3500-0
c,)ci)
2500
69
no es
Weight of Baby at Birth vs Bleeding
4080(02? 3980
En3880(0
>..3780Co
.6800
3580a)
3480
Bleeding
Figure 46
ivNutrientsAdditional nutrients that had a highly significant effect on birthweight wereMonofat, Monounsaturated Fatty Acids, Tol.Fol, Total folate (See Figure47) which had a positive impact on birthweight.
VitmnBl2, vitamin B 12 and glucose had a negative impact on birthweight.
The other nutrients in this regression were implicated but not highlysignificant with respect to birthweight i.e. vitamin C, Maltose, DietaryFibre, Copper, Cholesterol and Saturated Fatty Acids.
These and the preceeding nutrients together explain another 12.9% of thetotal variance in birthweight.
Weight of Baby vs Total Folate
0C)5000-
C) ça0
2000-
100200300400500600700Total Folate
=
Figure 47
70
11. ItFtL/ENCES ON INFANT GROWTH 41 ONE VEJ4R
11.1 METHOD OF ANALYSISThe regression techniques already described in 8.1 were also used in this section. Datawas available for 140 infants at one year. Weight alone is not the best indicator of babiesgrowth at one year as it gives no indication of whether the increment is lean body mass orbody fat. In addition weight and height are very highly correlated and this createsproblems in the regression analysis. As a result weight for height at one year was used asthe response variable as this was a better indicator of growth than either weight or heightalone.
11.2 RESULTSThere were 140 infants for whom complete data was available at 12 months after birth.On average the girls in the sample weighed 9.4kg, were 74cm long and had a headcircumference measurement of 46.6cm. The boys were longer, having an average weightof 10.3kg, height of 76.5cm and head circumference of 47.6cm (see Table 23). Theaverage weight for height was 131 standard deviation 13.1, range 104 to 171g/cm. Thedistribution of weight for height in gm/cm is given in Figure 32.
The basic regression model for babies growth at one year in terms of the weight for heightratio in g/cm is given in Figure 48, and an extended model is shown in Figure 49. Thebasic model contains only the most highly significant variables, whilst the extended modelincludes some less significant variables, but explains more of the total variance in growth.This latter model is included for interest as it provides an indication of other maternalfactors during pregnancy that may influence infant growth at one year. A summary tableshowing the build-up of the regression models is given in Table 28. The percentage ofgrowth, in terms of the weight for height ratio explained by each of the variables, as wellas their 95% confidence intervals and p values are shown in Table 29, for the basicregression model and Table 30 for the regression model. Selected lowess curves, intervaland box plots are provided in 11.3 to illustrate the effect of some of the variables ongrowth.
71
Basic Regression Analysis for Weight for Height at One Year
The regression equation isWt/ht = 89.5 + 0.00890 Wichange + 0.00891 Birth.Wt + 4.54 Sex.Baby
- 1.02 Brestfed + 17.0 Benefit + 16.0 Anaemia + 0.933 MUFA- 1.72 PUPA + 1.08 VitaminE - 0.0261 Cholest
107 cases used 90 cases contain missing values
PredictoCoefStdevt-ratiopConstant89.48709.367009.550.000Wtchange0.00890.002194.070.000Birth.Wt0.00890.001735.140.000Sex.Baby4.54202.051002.210.029Brestfed-1.02370.26690-3.840.000Benefit16.99005.956002.850.005Anaemia15.99903.918004.080.000MUFA0.93340.361502.580.011PUFA-1.71800.52740-3.260.002VitamjnE1.08010.574201.880.063Cholest-0.02610.01538-1.700.093
s = 9.849R-sq 54.8% R-sq(adj) = 50.1%
Analysis of Variance
SOURCE DFSSRegression1011300.1Error969311.3Total106 20611.4
MS- Fp1130.011.65 0.00097.0
Figure 48
72
Extended Regression Analysis for Weight for Height at One Year
The regression equation isWt/ht = 80.5 + 0.00862 Wtchange + 0.00861 Birth.Wt + 5.12 Sex.Baby
- 1.51 SESbefor + 30.8 Benefit - 0.932 Brestfed - 1.23 SESpreg- 1.73 Alcohol - 24.9 Dripstop + 14.6 Anaemia + 15.7 Ratiog/f- 0.0481 Sucrose + 2.87 Maltose + 0.648 MUFA - 1.83 PUPA+ 1.32 VitaminE - 0.0420 Cholest + 0.909 VitBl2 + 0.00473 Water
107 cases used 90 cases contain missing values
PredictorConstantWtchangeB irth.WtSex.B abySESbeforBenefitBrestfedSESpregAlcoholDripstopAnaemiaRatiog/fSucroseMaltoseMUFAPUFAVitaminECholestVitBl2Water
Coef80.51000.00860.00865.1210-1.510030.7670-0.9316-1.2286-1.7338-24.864014.580015.7260-0.04812.86600.6478-1.83351.3152-0.04210.90870.0047
Stdev12.95000.00210.00171.94900.58456.16400.24990.56400.84817.35303.67906.14800.04381.05500.33750.51460.63170.01480.44280.0030
t-ratio6.224.155.202.63-2.584.99-3.73-2.18-2.04-3.383.962.56-1.102.721.92-3.562.08-2.832.051.60
p0.0000.0000.0000.0100.0110.0000.0000.0320.0440.0010.0000.0120.2750.0080.0580.0010.0400.0060.0430.114
s = 8.782R-sq = 67.4% R-sq (adj) = 60.3%
Analysis of Variance
SOURCE DFSSMSRegression 19 13901.94731.68Error876709.4677.12Total10620611.40
Fp9.49 0.000
Figure 49
Table '8:Build-up of The Regression Analysis: Weight For Height at One Year
The regression equation isWt/ht = 82.2 + 0.00876 Wtchange + 0.0103 Birth.Wt + 3.22 Sex.Baby R2 = 26.1%
The regression equation isWt/ht = 98.4 + 0.00833 Wtchange + 0.00825 Birth.Wt + 4.99 Sex.Baby
- 1.28 Brestfed + 15.6 Benefit + 15.3 Anaemia R 2 = 49.6%
The regression equation isWt/ht 89.5 + 0.00890 Wtchange + 0.00891 Birth.Wt + 4.54 Sex.Baby
- 1.02 Brestfed + 17.0 Benefit + 16.0 Anaemia + 0.933 MUFA- 1.72 PUFA + 1.08 VitaminE - 0.0261 Cholest
Extended ModelFull basic model R'= 54.8%
The regression equation isWt/ht = 80.5 + 0.00862 Wtchange + 0.00861 Birth.Wt + 5.12 Sex.Baby
- 1.51 SESbefor + 30.8 Benefit - 0.932 Brestfed - 1.23 SESpreg- 1.73 Alcohol - 24.9 Dripstop + 14.6 Anaemia + 15.7 Ratiog/f- 0.0481 Sucrose + 2.87 Maltose + 0.648 MUFA - 1.83 PUPA+ 1.32 VitaminE - 0.0420 Cholest + 0.909 VitB 12 + 0.00473 Water
Extended model R 2 67.4%
74
Table 29:Table of Estimated Effects, Confidence Intervals and P-Values: Basic ModelFor Babies' Growth.
Variable Contribution* toEstimatedConfidence IntervalP-valueBaby's Growth (%)Effect
Lower Bound Upper BoundBirth.Weight 12.40.00890.00550.01230.000Weight Change 7.80.00890.00450.01330.000Sex.Baby 2.34.540.478.610.029Physical Variables 23.3Anaemia 7.816.0 8.223.80.000Breastfed 6.9-1.02-1.55-0.490.000Benefit 3.817.0 5.228.80.005Social Variables 19.5PUFA 5.0-1.72-2.76-0.670.002MLTFA 3.10.930.221.650.011VitaminE 1.61.08-0.062.220.063Cholesterol 1.4-0.026-0.0570.0040.093Nutrients 5.6Total Explained R2=54.8 (%) Unexplained45.2 (%)by the model (Error)
* The contribution quoted is the amount by which the R 2 (the percentage explained by the model)changes if that variable or group of variables is deleted from the final model. Note that since theexplanatory variables are correlated, the sum of individual contributions may add up to more or lessthan the combined effect of deleting a whole group.
75
Table of Estimated Effects, Confidence Intervals and P- Values:Extended Model
Contribution* toEstimated EffectConfidence IntervalBaby's Growth (%)
Table 30:
Variable
IDff
P-value0Lower Bound Upper Bound
Birth.Wt 10.1 0.00860.00530.01190.000Wtchange 6.5 0.00860.00450.01270.000Sex.Baby 2.6 5.12 1.25 9.000.010Ph ysical 27.7Benefit 9.3 30.8 18.5 43.00.000Brestfed 5.2 -0.93-1.43-0.430.000SESbefor 2.5 -1.51 -2.67 -0.350.011SESpreg 1.8 -1.23 -2.35 -0.110.032Alcohol 1.6 -1.73-3.42-0.050.044Social 18.0Anaemia 5.9 14.6 7.3 21.90.000Dripstop 4.3 -24.9-39.5-10.20.001Medical 10.5PUFA 4.8 -1.83 2.86-0.810.001Cholest 3.0 -0.042-0.072-0.0120.006Maltose 2.8 2.9 0.77 4.960.008Ratiog/f 2.5 15.7 3.5 27.90.012VitaminE 1.2 1.32 0.06 2.570.040VitB12 1.6 0.91 0.03 1.790.043MUFA 1.4 0.65-0.02 1.320.058Water 1.0 0.0047-0.0012 0.010.114Sucrose o.s -0.05-0.14 0.040.275Nutrients 11.9Total Explained R2=67.4(%) Unexplained32.6(%)by the model, (Error)
* The contribution quoted is the amount by which the R-squared (the percentage explained by the model)changes if that variable or group of variables is deleted from the final model.Note that since theexplanatory variables are correlated, the sum of individual contributions may add up to more or less thanthe combined effect of deleting a whole group.
76
11.3 DISCUSSION OF RESULTS
11.31 The Basic Regression ModelThe basic regression model accounted for 54.8% and the extended regressionmodel 76.8% of the total variance in infant growth at 12 months, expressed asweight for height. The significant variables will be discussed separately or ingroups.
Babies Birth weight, Birth. Wt. (See Figure 50)Birthweight is an important influence on growth to one year. For every1000g increase in birthweight there was an increase of 8.9g/cm in theweight for height ratio (95% CI +5 to +12 g/cm).
Babies' Growth vs Babies' Weight at Birth
170
160-c0) 150ci)
140.c.9 130(1)
120
110
Ic
fffm2000300040005000
Weight of Baby at Birth (gms)
Figure 50
Weight Change from Birth to 6 Weeks, Wtchange.Most babies increased in weight between birth and 7 weeks by on average131 lg, standard deviation 496g, with an actual range in weight changefrom a loss of -70g to a gain of 2632g. The coefficient for this weightchange variable was surprisingly the same as that for birthweight, ie, forevery I000g increase in weight between birth and 6 weeks, there was anincrease of 8.9g/cm (95% CI +4.5 to +13.2). This variable is not asimportant as birthweight as the range of weight gain from birth to 6 weeksis much smaller than the range in birthweight.
iii.Sex of Baby, Sex.Baby.It has already been shown in Section 7 that boys are generally heavier andtaller than girls at one year. This variable is coded 0 for female babies andI for male babies. This means that the weight for height ratio for malebabies at one year is on average 4.5g/cm greater than that of female babies(95% CI 0.5 to 8.6g/cm).
77
-z0w>
I155
145
iK11
125
These three anthropometric variables - i, ii, and iii account for 26.1 % of the totalvariance and almost half the variance that is accounted for in the main model.
iv.Length of Breastfeeding in Months, Brestfed. (See Figure 51)Breastfeeding had a negative impact on growth in terms of the weight forheight ratio. In general the longer the infant was breastfed, the lower theweight for height ratio. However, this ratio does not distinguish betweenfat and lean body mass. In most cases the lower weight of the breastfedinfants was probably due to lower body fat levels. For every month theinfant was breastfed the weight for height ratio decreased by on averageI g/cm (95% CI - 1.5 to -0.5g/cm), compared to bottle-fed babies.
For an average baby at one year, one would expect the weight to heightratio in the breastfed baby to be 12.2g/cm less than bottle-fed baby. Thismeans that if an average baby was breastfed for 12 months it could beexpected to have a weight to height ratio of 119 whereas if it was bottle-fed for this period, its weight to height ratio would be 131 (this assumesthe length of the baby is the same).
Weight/Height at 1 Yr vs Breastfeeding
0123456789101112Length of Breastleeding (months)
Figure 51
V.Mother on Benefit Only, Benefit. (See Figure 52)The sole source of income for mothers in this group was the DPB,Unemployment Benefit, Sickness or ACC Benefit. This is a Yes=], No=Ocoded variable. Infants whose mothers were on a benefit had a weight toheight ratio on average 17g/cm greater than infants whose mothers werenot on a benefit (95% CI +5.1 to +28.8glcm). Most of the mothers on abenefit bottle fed their babies so this increased weight to height ratioprobably indicated greater bod y fat levels in these children.
[78
No Yes
Weight/Height at 1 Yr vs Mother On A Benefit
U)r
160
I:Mother On A Benefit
Figure52
vi.Mothers with anaemia during pregnancy, Anaemia. (See Figure 53)This is another Yes=], No=O coded variable. Infants born to mothers withanaemia had an average weight to height ratio I 6glcm greater than infantsborn to normal mothers (95% CI +8 to +24g/cm). We have noinformation to indicate whether this anaemia diagnosis is 'real' or a resultof the haemodilution of pregnancy. A greater increase of blood fluid,volume is associated with higher birthweight babies. This study has shownthat higher birthweight babies also have a higher weight to height ratio at Iyear. This finding is worthy of further investigation.
The last 3 factors (iv, v and vi) account for 23.5% of the total variance in weightfor height at 12 months.
Weight for Height at 1 yr vs Anaemia
U)
150
140wI0
-C
130
No Yes
Anaemia in pregnancy
Figure 53
29
Vii. Nutrient Intake of the Mother During Pregnancy; MonounsaturatedFatty Acids, MUFA, Polyunsaturated Fatty Acids, PUFA, Vitamin Eand Cholesterol, Cholest.Overall, maternal nutrient intake during pregnancy accounted for 5.2% ofthe total variance in weight for height at one year. Whether this effect wasactually caused by some influence of maternal diet during pregnancy on thefoetus itself, or whether maternal diet during pregnancy is an indicator ofthe type of food fed the infant from when solids were started is not known.The latter explanation would seem more likely.
Average MUFA intake by the mothers during pregnancy was 28g/day,(range 10 to 58). For every gram increase in MUFA in the maternal diet,the weight to height ratio increased by 0.9g/cm (95% CI +0.2 to +1.6).This effect is substantial when the diets of mothers with high and lowMUFA intakes is examined. Mothers with high MUFA intakes consumedon average 46g of MUFA/day as against 16g/day in women who had lowMUFA intakes. This equates to 41.4g/cm of weight to height ratio beingattributed to high MUFA intakes and 14.4g/cm to low. Mothers with highMUFA diets had high energy intakes, takeaways 6-8 times/16 days, atemeat (often high fat) daily, moderate intakes of dairy products, cakes andbiscuits, nuts and avocado, and high intakes of fried foods. Women withlow MUFA intakes had much lower energy intakes (8.7 MJ was thehighest) and much lower intakes of the above foods.
In contrast PUFA intake had a negative impact on weight for height at oneyear. Mean PUFA intake by the mothers was 9.3g/day. Women with highPUPA intakes consumed on average 21.5g/day which equates to anaverage drop in the height to weight ratio at one year of 36g/cm (Ic,-1.7g/cm for each g of PUPA, (95% CI -2.8 to -0.7). Most of thesewomen had high energy intakes, used PUFA margarine as a spread, oftenused PUFA containing mayonnaise, as well as consuming large amounts ofcakes and biscuits and moderate amounts of takeaways and fried foods.Women with low PUFA intakes had low energy intakes and consumed onaverage 5.4g of PUFAJday. These women all used butter as a spread andhad low fat intakes.
Cholesterol intake also had a negative impact on weight at one year.Average cholesterol intake was 289g/day. Women with high intakesconsumed on average 526g/day which equated on average to a decrease of13.7g/cm in the height to weight ratio at one year (ie, -0.02g/cm for each gof cholesterol) (95% CI -0.06 to +0.004). Again these women generallyhad high energy intakes, consumed meat daily in large serves (eg, 112g ofmince and 450g of chicken in one day), ate 10 to 18 eggs/16 days and hada moderate intake of dairy products.
This is an interesting set of conflicting results as high MUFA diets areoften high in PUFA and sometimes cholesterol also. For every mgincrease in Vitamin E intake weight for height ratio at 1 year increased by
80
I .08g/cm (95% CI, -0.05 to +2.2 g/cm). The average Vitamin E intake ofthe women was 8.7mg range 3 to 22 mg/day.
All the significant nutrients in this analysis were lipids, mostly unsaturated,and the antioxidant Vitamin E. The impact of the highly unsaturatedPLJFA is negative and that of the antioxidant Vitamin E is positive. Is thisjust coincidence? Or are we seeing an increased requirement of Vitamin Eto prevent cell membrane oxidation?
11.32 The Extended Regression ModelThe extended model accounted for 76.8% of the total variance in growth in termsof weight for height at 1 year. As well as the variables included in the main model,additional variables in this model were;
i.Socioeconomic Status of Mother's Occupation Before Pregnancy, SESMum 1.Socioeconomic Status of Mother's Occupation During Pregnancy, SESMuin2.The lower the socioeconomic status of the mother, the lower the weight toheight ratio of the infant (see Figure 54). Mothers who did not work anddid not receive a benefit, and mothers who were on a benefit had babieswith the highest weight to height ratio (7 in Figure 54).
Weight/Height at 1 yr vs SES During Pregnancy
(0r 137C0
132
0)127
0
122
123456 A1HomeMothers SES During Pregnancy
Figure 54
181
-C
13Ec\jCt,
-c,127
CDI0
122
ii.Usual Alcohol Intake Before Pregnancy, Calculated in Terms of ZeroTime Blood Alcohol Level, Alcohol].Alcohol Intake During Pregnancy, Coded in Terms of the Frequency ofDrinking, A lcohol2.Alcohol intake, especially alcohol intake before pregnancy, and presumablyafter birth had a highly significant negative impact on growth. A numberof these mothers were breastfeeding at one year.
Hospitalised for Toxaemia, Toxemia]Medicated for Toxaemia, Toxemia2.Toxaemia has a negative impact on weight for height at one year. Thiscould be an example of an insult on foetal development carrying through tolater life.
iv.Significant Nutrients.Glucose to Fructose Ratio, GLU/Fru.SucroseMaltoseVitamin B 12 , Vit.B12.Weight of water in the diet (not including drinking water), Water.
For interest graphs to show the effect on weight for height at one year of motherssmoking during pregnancy (Figure 55), asthma during pregnancy (Figure 56) and diabetesduring pregnancy (Figure 57) are included below.
Babies Growth vs Mother Smoking
No YesDid the Mother Smoke?
Figure 55
182 U
(I,-zz0
C)
I—(C
-c0)C)I0
0)C)
133
128
123
118
Weight/Height at 1 Yr vs Mothers Asthma
No Yes
Mothers Asthma
Figure 56
Babies Growth vs Mother with Diabetes
(0
128
No Yes
Did the Mother Have Diabetes?
Figure 57
83
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33. Beaton, G.H., Milner, J., McGuire, V., Feather, T.E., Little, J.A. Sources of variance in24-hour dietary recall data: implications for nutrition study design and interpretation.Carbohydrate sources, vitamins and minerals. Am. J. Clin. Nutr., 1983; 37, 986-995.
34. Todd, K.S., Hudes, M.S., Calloway, D.H. Food intake measurements: problems andapproaches. Am. J. Clin. Nutr., 1983; 37, 139-146.
35. Liu, K., Stamler, J., Dyer, A., McKeever, J., McKeever, P. Statistical methods to assessand mimimize the role of intra-individual variability in obscuring the relationship betweendietary lipids and serum cholesterol. J. Chron. Dis., 1978; 31, 399-418.
36. Van Raaij, J.M.A., Vermaat-Mjedema, S.H., Schonk, C.M., Peek, M.E.M., Hautvast,J.G.A. Energy requirements of pregnancy in the Netherlands. Lancet 1987: ii 953-5. 0
37. Prentice, A.M., Goldberg, G.R., Davies, H.L., Murgatroyd, P.R., Scott, W. Energysparing adaptations in human pregancy assessed by whole-body calorimetry. Br. J. Nutr.,1989; 62, 5-22.
38. Naeye, R.L. Maternal body weight and pregnancy outcome. Am. J. Clin. Nutr., 1990;52, 273-9.
Elley, W.B., and Irving, J.C., The Elley-Irving Socio-Economic Index 1981 CensusRevision, NZ J.Ed.Stud., 1985, 20, 115-128.
Irving, J.C., and Elley, W.B., A Socio-Economic Index for the Female Labour Force inNew Zealand, NZ. J. Ed. Stud., 1977, 12, 154-163.
Food and Nutrition Guidelines for Healthy Pregnant Women, A Background Paper,Public Health Commission, 1995, Wellington.
Food for Health Report of the Nutrition Task Force, Department of Health, 1991,Wellington.
Watson, P.E., Total Body Water and Blood Alcohol Levels: Updating the Fundamentals,Human Metabolism of Alcohol, Eds., Crow, K.E., Batt, R.D., CRC Press, Florida, 1989.
IIa
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43.
86
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13. APPENDIX ONEDistribution of Nutrient Intake at Month 4 and Month 7 of Pregnancy
V V20040060080010001200140016001800
20040060080010001200140016001800
Cal cium (mg) -4th month
V V20040060080010001200140016001800
Mean- - QuartileV RNI(pregnant
V RNI (adults)
20040060080010001200140016001800
Calcium (mg) - 7th month
187
ci
VV V5 79111315171921IIIIIIII -- $30 -II
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579111315171921
lron(mg) - 4th monthMean
I QuartileV RNI(pregnant
VVy V RNlrangeU
46810121416182022 (adults)
IIIJIIIII30I ElIIII(I)
- I1 UC)9o — i
IIC/)'4- I
___ El0 IICC)2 10-
C) II [1CL i 1
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IIIIIIIII4 6810121416182022
lnn(mg) - 7th month El
U
ci
ci
188ci
89
VV
VV10002000 30004000500060007000
1000200030004000500060007000
Sodium (mg)-4th month
V V
V V10002000300040005000600070008000
Mean- QuartileV RNI(pregnant
V RNI (adults)-ranges
10002000300040005000600070008000
Sodium (mg) -7th month
20U)
110
0
40
U)
0
20CD
(1)Dio
0
V V
V V1000 1500 2000 2500 3000 3500 4000 4500 5000 Snon
10001500 2000 2500 3000 3500 4000 4500 5000 5500
Potassium (mg) - 4th month
V V
V V10002000300040005000
Mean- QuartileV RNI(pregnantV RNI(adults)
-ranges0 60007000
01000200030004000500060007000Potassium (mg) - 7th month
90
20co0C)
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0.10C)2U)0
0
20
co0C)
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0
1
V V.
V V1000 1500 2000 2500 3000 3500 4000 4500 5000 5500
V V
V V1000200030004000500060007000
- Mean- - Quartile
V RNI (pregnant
V RNI (adults)-ranges0
01000200030004000500060007000
Potassium (mg) - 7th month
1000 1500 2000 2500 3000 3500 4000 4500 5000 5500Potassium (mg) - 4th month
20
U)
0
20Cl)0Q)
U)'4-0.10U)U)0
0
40
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0
L1cI LII
V RNI(pregnant
V RNI(adults)V V2.55.07.510.012.51 fl17
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5791113151719Zinc (mg) - 4th month
Mean £3- -
5.07.510.012.515.017.520.022.525.0Zinc (mg) - 7th month
92
VT020406080100120140
020406080100120140
Selenium (mg) - 4th month
VT020406080100120
- Mean- - QuartileV RNI(pregnant
V RNI(adults)
020406080100120
Selenium (mg) - 7th month
193
40
to4-00)30YTC,)°20
o10
0
50
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CL 10
0
20
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0
U
IJVT0.50 0.751.001.251.501.752.002.25 2.50 2.753.00IIIIIIIII
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IIIIiIIIIIEl0.50 0.751.001.251.501.752.002.25 2.50 2.753.00
Thiamin (mg) - 4th monthMean
- QuartileU
VT0.00.51.0
V RNI(pregnantV RNI(adults)
1.52.02S
0.51.01.52.02.53.03.5Thiamin (mg) - 7th month
1
VT0.51.01.52.02.53.03.54.0
0.51.01.52.02.53.03.54.0
Ri bof I aA n (mg) - 4th month
VT0.51.01.52.02.53.03.5
- Mean- - QuartileV RNI(pregnant
V RNI(adults)
0.51.01.52.02.53.03.5
Ri bofi avi n (mg) - 7th month
95
40
C))—30
(I)520
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40
C') 300C)
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C) 10ci
0
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ni
50
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0
0U
cici13UU
Mean11- QuartileYRNI(pregnant U-ranges
ci
UI3ci11ci
ciUED
i2025303540455055Niacin equilent (mg) - 4th month
iu203040506070Niacin equivalent (mg) - 7th month
15202530354C)A
97
vvTV
0.51.01.52.02.53.03.54.04.5
0.51.01.52.02.53.03.54.04.5
Vitamin B6 (mg) - 4th month
vv
TV0.51.01.52.02.53.03.54.04.55.0
- Mean- - QuartileV RNI (pregnantV RNI (adults)
-ranges
0.51.01.52.02.53.03.54.04.55.0
Vitamin B6 (mg) - 7th month
0
40
C')10020
-10
35
30C,)
25
20
.15
IL
0
'7,050100150200250Inn
U50100150200250300350400Vitamin C (mg) - 4th month
0 v 50V 1001502002500011 cI
— Mean
— - Quartile
RNI(pregnant
V RNI(adufts)
050100150200250300350400Vitamin C (mg) - 7th month
30
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0
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0
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Es
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0
30
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846810121416182022
46810121416182022Vitamin E (mg) - 4th month
Mean- - QuartileV RNI (pregnantV RNI (adults)
2.55.07.510.012515.017.520022
2.55.07.510.012.515.017.520.022.5Vitamin E (mg) - 7th month
1100
I701
100150200250300350400450500550Cholesterol (mg) - 4th month
- Mean- - Quartile
100150200250300350400450500550
100200300400500600700800
100200300400500600700800Cholesterol (mg) - 7th month
30
(I)
10210C)0
0
40
C,)F0204-
C)2(1) 10
0
30
U)C-)a)
20C/)
0
C
10CL
0
30
U)I-C-).,200
C')
0
Ca) 10
ci)0
0
51015209 c
- u2530354045Dietary fibre (g) - 4th month
- Mean
- - Quartile
51015202
O253035404550Dietary fibre (g) - 7th month
F- 102
90
80
70
> 600
50
0- 40C)U.. 30
20
10
0
80
70
60>0 50CC)
400- 30U-
20
10
0
4th month
253035404550
% of total energy from fat
7th month
25303540455055
% of total energy from fat
103
0100020003000400050006000
Total vit. A equiv. (ug) - 4th month
r' _-.-7 _f: r(
50
Cl) 400.a)-Q
30Cl)9-0
20CD0a)0_10
90
80
700a)Cl) 509-04-
30
Q20
10
0
V'V
500 1000 1500 2000 2500 3000 3500 4000 4500 5000
500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Total vit. A equiv. (ug) - 4th month
VV
0100020003000400050006000
tJUUUUUU
.9Mean[]Quartile
'V RNI (pregn[];V RNI (adults)
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