Introduction

Theperiodofintrauterinegrowthanddevelopmentis one of the most vulnerable periods in the humanlife cycle. The weight of the infant at birth is apowerfulpredictorofinfantgrowthandsurvival,andis dependentonmaternal health andnutritionduringpregnancy. Low birth weight (LBW) is defined as weighing less than 2,500 g at birth. In developingcountries, including India, the majority of LBW infants becauseofintrauterinegrowthretardation(IUGR)areborn small at term (> 37 wk of gestation) with only

Maternalnutrition&lowbirthweight-whatisreallyimportant?

SumithraMuthayya

Division of Nutrition, St. John’s Medical College & Research Institute, St. John’s National Academy of Health Sciences, Bangalore, India

ReceivedApril24,2009

The prevalence of low birth weight (LBW) is higher in Asia than elsewhere, predominantly because of undernutrition of the mother prior to and during pregnancy. There are qualitative differences in dietary requirements during early and late pregnancy - micronutrients and proteins required in early pregnancy, and calories and other nutrients later. A paradigm shift from efforts to improve size at birth, to efforts to improve foetal growth and development might provide fresh insight into the problem. Micronutrient deficiencies during pregnancy have been shown to have serious implications on the developing foetus. Nearly half the pregnant women still suffer from varying degree of anaemia, with the highest prevalence in India, which also has the highest number of maternal deaths in the Asian region. Of specific concern is compliance with iron supplementation, cultural beliefs regarding diet in pregnancy, and the issue of nutrition supplementation and fortification. The coexistence of risk of LBW or intra uterine growth retardation (IUGR) associated with essential fatty acid docosahexaenoic acid (DHA) and vitamin B12 intake or status observed in the Indian sub-continent also requires further examination. There is a significant protective effect of higher maternal education (beyond high school). Optimal weight gain during pregnancy and a desirable foetal outcome may be a result of synergisitic effects of improved food intake, food supplementation, improved micronutrient intake, education and the environment of the pregnant woman and her family.

Key wordsEducation-energy-IUGR-lowbirthweight-maternalnutrition-micronutrients

6.7percentbornprematurely.Lowbirthweightleadstoanimpairedgrowthoftheinfantwithitsattendantrisksofahighermortalityrate, increasedmorbidity1,impairedmentaldevelopment2,andtheriskofchronicadult disease3. Infants who weight 2,000-2,499 g atbirthhaveafour-foldhigherriskofneonataldeaththanthosewhoweight2,500-3,499g.Themoreseverethegrowth restriction within the LBW category, the higher is the risk of death1. LBW is a strong predictor for sizeinlater lifebecauseIUGRinfantsseldomcatch-uptonormalsizeduringchildhood4.otherimportant

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causescouldincludematernalinfections,lowmaternalnutrientintake,highernutrientlosses,and/orincreasednutritional requirements during pregnancy5. Maternalnutrition is an important factor from a public healthpoint of view because it is modifiable and therefore susceptible to public health interventions. There is,therefore,anurgentneedtodeterminewaysandmeansto prevent LBW and its consequences. This paper reviews maternal nutritional and socio-economicfactorsandtheirroleinlowbirthweightandIUGR.

Maternal anthropometry and pregnancy outcome

The causesof lowbirthweight are complexandinterdependent, but the anthropometry of the motherandhernutritionalintakearethoughttobeamongthemost important. Pre-pregnancy weight, body massindex (BMI) and gestational weight gain all havestrong, positive effects on foetal growth suggestingthatenergybalanceisanimportantdeterminantofbirthoutcomes6,7. The WHO collaborative study on maternal anthropometry and pregnancy outcomes, using datafrom111,000womenfromacross theworldreportedthat mothers in the lowest quartile of pre-pregnancyweight carried an elevated risk of IUGR and LBW of2.55(95%CI2.3,2.7)and2.38(95%CI2.1,2.5)respectively,comparedtotheupperquartile.Attainedmaternalweightat20,28or36wkofgestationshowedevenhigheroddsratiosforIUGRof2.77,3.03and3.09respectively when women were compared betweenquartilesofhighest tolowestattainedweight.Thisispossiblybecauseitconsidersweightgaininpregnancyincluding that of the foetus. Women in the lowest quartile for both pre-pregnancy weight and weightgainduringpregnancywerefoundtobeathighestrisk(up toweek20,oR5.6; up toweek36,oR5.6) ofproducinganIUGRinfant7.AstudyinIndiareportedthe odds ratio for LBW among Indian mothers to be three times more in severe chronically energy deficient (CED) low BMI groups when compared to normalBMI groups8.A prospective pregnancy cohort studycarried out in Bangalore, India, confirmed that a low maternalweightatbaselineandpoorweightgaininthesecond trimester tobe important predictorsof IUGRaftercontrollingforpotentialconfoundingvariables9.Low maternal body weight had an association withhigher risk of IUGR of marginal significance (AOR: 1.62;95%CI:0.83,3.15;P=0.09).Therewasaverystrong inverse association between weight gain perweek during the second trimester and IUGR in bothunivariate and multivariate analyses. Compared withwomen in the highest quartile, the adjusted odds of

IUGR was higher in women in the first quartile (AOR: 3.98;95%CI:1.83,8.65),secondquartile(AoR:2.07;95% CI: 0.94, 4.53) and third quartile (AoR: 1.32;95% CI: 0.58, 3.03). Weight gain per week in the secondtrimesterwas<0.3kgin70percentofmotherswhodeliveredIUGRbabies.Lowerweightgainedinthethirdtrimesterwasnotassociatedwithhigherriskof IUGR.Thisstudydemonstrated thata lowweightgain for even brief periods during pregnancy placesthe foetus at risk for IUGR9. Abrams and Selvin10also demonstrated that low maternal weight gain inthe second trimester (<5.7 kg) was associated withdecreased birth weights ranging from 48 to 248 g,dependingon thepatternofweightgain in theothertrimesters. Clearly improving maternal weight priortoconceptionandpregnancyweightgainarepotentialstrategiestoimprovebirthweight.

Effect of socio-economic status

Studies worldwide have examined the effect ofsocio-economic status (SES) indicators, includingmaternal education, on birth weight and IUGR.Maternal illiteracyand lowSEShavebeenshown tobemajorriskfactorsforIUGR11,12.Inthedevelopingworld,lackingproperhealthsystemsandresources,thelevelofmaternaleducationmaybeofprimeimportancein the determination of health outcomes of mothersandtheirinfantsandchildren.IntheBangalorecohortstudy,adecreasingtrendofIUGRwasobservedwithanincreaseinmaternaleducation,rangingfrom46percentinwomenwhohadnoschoolingto19percentinwomenwhohadapost-graduateeducation(T.Sarah,unpublished observations). In addition, the odds ofIUGRforwomenwithahighschooleducationorbelowwas1.5(95%CI:1.04,2.17)whencomparedtothosewithpre-universityeducation,therebyunderliningtheimportanceofmaternaleducationindeterminingahostofhealth-relatedbehaviour/practices.Itisimportanttounderstandthatwhileachievingtheuniversalprimaryeducation is laudable for India, promoting educationto higher levels should be the ultimate goal. Factorsrelatingtothecareofwomen,environmentalhygieneand sanitation, household food security, and povertyarealllikelytooperatesimultaneouslywithalowlevelofmaternalliteracyintheaetiologyoflowbirthweightandIUGR.

Macronutrient supplementation during pregnancy

An adequate nutrient supply to the foetus isan important area of research while investigatinginterventions to enhance birth weight. There is

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controversy on whether dietary macro- and micro-nutrient supplementation in pregnancy can increasebirth weight. A meta-analysis showed only modestincreases in maternal weight gain and foetal growthfollowingdietarysupplementation13.

Evidencefromsystematicreviewsofrandomizedcontrolled trials on the effectiveness of nutritionalinterventionsaimedatreducingIUGRhasdemonstratedthe beneficial effects of macronutrient (protein/energy) supplementation,withanoveralloddsratioof0.77(95%CI0.58,1.01)forreducingIUGR14.Supplementationwas associated with increases in maternal weightgain and mean birth weight, and a decrease in thenumber of LBW babies of borderline significance. A community based trial in rural Gambia showed thatsupplementing pregnant women with a high-energygroundnut snack significantly increased birth weight15.Supplementation significantly increased birth weight (by 136 g, P<0.001). Birth length was not affected.The effect of supplementation on birth weight wasprimarilyachievedthroughareductioninthenumberofbabieswhowere“smallfortheirdates,”ratherthana reduction in prematurity, as gestational age wasnot affected. over the whole year, supplementationreducedtheprevalenceoflowbirthweightfrom17.0to11.1percent.However,dataontheeffectsofmaternalmalnutritiononbirthoutcomesin797mothersinruralIndiafoundnorelationbetweenmaternalenergyandprotein intake, but instead demonstrated a strongerrelationship with dietary intake of micronutrient-richfoods16.

Effect of vitamin B12 and folate

Recently, interest has turned to specific micronutrients as possible limiting factors for foetalgrowth. The effect of micronutrients in significantly decreasing the risk of low birth weight has alsobeen demonstrated in randomized trials of multiplemicronutrient supplementation of HIV-infectedpregnant women in Tanzania17 and more recentlyin pregnant mothers in Nepal18. Data concerning theeffects of maternal malnutrition on birth outcome inrural Indiahavebeenreported inaprospectivestudyof 797 rural Indian mothers, where birth size wasstronglyassociatedwith consumption, atweek28ofgestation, of green leafy vegetables (P<0.001) andfruits (P<0.01) even after adjustment for potentiallyconfoundingvariables16.Erythrocytefolateatweek28ofgestationwasalsopositivelyassociatedwithbirthweight(P<0.001)withnoassociationbetweensizeatbirthandmaternalenergyandproteinintake.

GreaterclarityonthedeterminantsofIUGRwouldbe obtained by the study of a more heterogeneouspopulation, varied in their demographics, socio-economicstatus,accesstofoodandvariabilityofactualfoodintake,asituationlikelytoexistinurbanwomenindevelopingcountries.DatageneratedfromthecohortofpregnantwomeninurbanBangalore,India,showedthatwomeninthelowesttertileforserumvitaminB12concentration during each of the three trimesters ofpregnancy had significantly higher risk of delivering anIUGRbaby(AoR,5.98,9.28and2.81fortrimesters1- 3, respectively),when compared towomen in thehighestfertile9.AnintriguingpossibilityisthatofpoorbioavailabilityoforalvitaminB12 intake.Anearlierstudy reported negative correlations between birthweightandmaternalvitaminB12levelsatdeliveryinsmokers in a Western group of women19.Anassociationbetween low serum and amniotic fluid concentrations ofB12andneuraltubedefectshasalsobeenreported20.It is now known that the prevalence of vitamin B12deficiency is high in the Indian population, with metabolic evidence of deficiency in 75 per cent of young urbanIndianmenandwomen,inwhomlessthan5percent had both folate deficiency and anaemia21.ItmaybeimportanttolookintothepotentialroleofvitaminB12deficiency in elevating plasma homocysteine (Hcy) levels in pregnancy, and its implications for adversepregnancy outcomes including low birth weight22.Methionine synthase is an enzyme which catalyzesthemethylationofhomocysteinetomethionineusingvitaminB12asacofactorandmethyltetrahydrofolateasasubstrate23.Formationofmethioninethroughthispathway represents an important component of theone-carbonmetabolismforsynthesisofphospholipids,proteins, myelin, catecholamines, DNA and RNA.Adeficiency of either vitamin B12 and/or folic acid is likely toaffect thispathwayresulting inanelevationofplasmaHcywitharelativelylowmethioninelevel.Murphyet al24havereportedthatmothersinthehighesttHcy(totalhomocysteine)tertileat8wkofpregnancyhadthreetimes(oR:3.26;95%CI:1.05,10.13)andat labor had nearly four times (oR: 3.65; 95% CI:1.15, 11.56) the odds of giving birth to a neonate inthe lowestbirthweight tertile.Additional studies areneeded to elucidate the role of vitaminB12 togetherwith homocysteine in the prevention of adverseoutcomes,particularlyIUGR.

Vitamin B12 concentration in the neonate (cordserum) was significantly higher than, but correlated to levelsinthemother,atalltrimestersofpregnancy25,26.

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Ingeneral,bothmaternalandfoetalvitaminB12levelsin Indians were lower than that reported in westernsubjects25,26; thismaybelinkedto their lowerdietaryvitaminB12intakeashasbeensuggestedinovo-lactovegetariansandlow-meateaters.CordserumvitaminB12levelswerelinearlyassociatedwithbirthweight,such that increasingcord levelswereassociatedwithincreasing birth weight. An interesting associationhasalsobeenobservedbetweenbirthweightandcordserum B12 of term infants with a gestational age of37-39wk,butnotininfantswhoweredeliveredat>40wkgestation26.Itisknownthataspregnancyextendspost-term, the incidence of placental insufficiency and foetalpostmaturity(dysmaturity) increasesrapidlyasa consequence of reduced respiratory and nutritiveplacental function27. Postmaturity is correlated withan increased incidence of placental lesions, foetalhypoxia-asphyxia, intrauterine growth retardation,increasedperinatal death, andneonatalmorbidity.Atthebiochemicallevel,placentalphysiopathologyinpostterm-postmaturepregnancies isnotwellunderstood,however, it can be speculated that the relationshipbetweenbloodnutrient levelsandbirthweightmightbeconfoundedbypoorplacentalfunctioninlatetermpregnancies.

Iron status and pregnancy

Iron deficiency is the most commonly recognized nutritional deficiency in both the developed and the developingworld.Itisestimatedthat<50percentofwomendonothaveadequateironstoresforpregnancy.Requirements for absorbed iron increase duringpregnancy from 0.8 mg/day in the first trimester to 7.5 mg/day in the third trimester. Average requirementduring the entire gestation is approximately 4.4 mg/day. An adequate iron balance during pregnancyimpliesbodyironreservesof>500mgatconception.Thephysiologic ironrequirements in thesecondhalfof gestation cannot be fulfilled solely through dietary iron28. Iron deficiency anaemia has been shown to be associated with low birth weight and pretermdelivery29,30. Data from Shanghai suggested that theeffect of maternal anaemia on preterm delivery wasthe most detectable during the 1st trimester, beforematernalplasmavolumeexpanded31.

Themechanismsthatoperatebywhichpoorironstatus may affect birth weight and preterm birthsremains poorly understood.A few tested hypothesesare (i) poor iron status may affect immune functionadversely and thus increase thehost susceptibility to

genital tract infections, (ii) iron deficiency may increase the stresshormonesnorepinephrineandcortisol, (iii)low haemoglobin concentrations may cause chronichypoxia,whichcanactivatethebody’sstressresponseandthusincreasecirculatinglevelsofcorticotrophin-releasing hormone, and (iv) iron deficiency may increase oxidativestressoftheplacenta32.Randomizedtrialsofironprophylaxisduringpregnancyhavedemonstratedpositive effects on reducing low haemoglobin andhaematocrit,andincreasingserumferritin,serumironandothermeasures,includingbonemarrowiron33.

A placebo-controlled study from Nepal with ahigh prevalence of iron deficiency demonstrated that asupplementof60mgof ferrous ironand0.4mgoffolic acid daily from 11 wk gestation significantly increasedthebirthweight34.Aplacebo-controlledstudyfromClevelanddemonstratedthat30mgofferrousirondaily in pregnancy, started before 20 wk of gestation,gave a significantly higher birth weight compared with theplacebogroup35.Theresultsofthesestudiessuggestthat toobtainamaximumeffectonbirthweight, ironsupplementsshouldbestartedinearlypregnancy29,34,35.However, evidence is insufficient to prove that iron deficiency plays a causal role in poor pregnancy outcome36. The debate concerning prophylactic ironsupplementationtopregnantwomenisstillcontroversialandthereexistsnoconsensusonthisimportantissue.

Effect of essential fatty acids

Docosahexaenoic acid (DHA; 22:6n-3) andarachidonicacid(AA;20:4n-6)areessentiallongchainpolyunsaturatedfattyacids(LCPUFA)ofthen-3andn-6familiesthatareimportantstructuralconstituentsofthehighlyspecializedmembranelipidsofthebrainandthehumancentralnervoussystem,criticalfornormalgrowthanddevelopment.DHAisparticularlyfoundinthemembranesofneuronalsynapsesandintheoutersegmentsofretinalrodsandconeswhereitconstitutes50percentof the totalPUFA37,38.Duringpregnancy,accretion of maternal and foetal tissues occurs andconsequentlytheLCPUFArequirementsarehigh.Thedevelopinghumanfoetusaccumulatesasmuchas400mg DHA per week during the last trimester39, mostof which is incorporated into the structural lipids ofthedevelopingbrain40-42.Because the foetusdependsprimarilyonplacental transferof these fattyacids, itisimportantthatmaternalLCPUFAstatusandsupplyisadequatetomeetfoetalrequirements43.Intheearly1990s, positive associations between maternal fish intake andbirthweightwerefoundduringpregnancyinDanish

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fish eating communities44,45. In the same population,olsenandSecher46morerecentlydemonstratedastrongnegative association of fish intake with the risk of both low birth weight and preterm delivery. PopulationsthatconsumelargelycerealbaseddietswithlittleornoseafoodsuchasinIndia,dependontheconsumptionofplant sources of essential fatty acids (EFA), α-linolenic acid (ALA; 18:3n-3) and linoleic acid (LA;18:2n-6)and their endogenous conversion to DHA and AA,respectively.However,thereisevidencetosuggestthatthere may be an inefficient conversion of ALA and LA to their respectiveLCPUFAsand thatbothALAandLAcompete for the samedesaturation andelongationenzymesforconversiontoDHAandAA47,48.RecentdataalsosuggestthattheabsoluteamountsofALAandLAinthedietdetermineALAconversioninthebody49,andnot their ratio,aspreviouslybelieved50.Consequently,theadequateconsumptionoffoodsourcesrichinbothn-3 and n-6 fatty acids may be important to maintaintheirstatusinthepregnantmother.InBangalore,southIndia, overall intakes of fish and of DHA and AA were verylow51. Median fish intakes were about 5-10 times lowerthanthosereportedinDanishpregnantwomen46.Consequently,longchainn-3fattyacidintakeswerealsoproportionallylower(by100foldormore)thaninthedietsofwesternpregnantwomen.Muthayyaet al51alsofoundincreasesofbetween100and200ginbirthweightbetween the lowest and highest fish/ DHA intake groups. Women who did not eat fish during the 3rd trimester had a significantly higher risk of LBW (OR: 2.49, P=0.019).Similarly,lowEPAintakeduringthe3rdtrimesterhadan association with a higher risk of LBW (OR: 2.75, P=0.011).Lowmaternalintakesoffattyacidsthatarecriticalforfoetalgrowthanddevelopmentareamatterofconcerninthispopulation.Thisunderlinestheneedforfurtherinvestigationofthepotentialofmarinefoodsand/orn-3PUFAinimprovingfoetalgrowthinIndia,wherelowbirthweightaffectsnearly30percentoftheinfants7.DHAandAAconcentrationsareincreasedinthe foetal circulation because of preferential transferby the placenta from the mother to the foetus52.Thefoetus is also able to synthesize DHA from its fattyacid precursor; however, this ability (measured soonafter birth) may be impaired in IUGR infants53. Themechanism of action of DHA in improving foetalgrowth may be linked to its effect on endothelium54.DHA increases flow mediated vasodilation in young adults55, and improves membrane receptor activityprobably through improvements in membranefluidity56.Therefore,itispossiblethatthesefattyacidsmayincreasefoetalgrowthratebyincreasingplacental

blood flow through the ratio of biologically active prostacyclins to thromboxanes and reduced bloodviscosity57.

Body composition of the neonate

InIndianinfants,increasingbirthweightmustbeevaluated with regard to their body composition atbirth,sincetheyarethoughttohaveasimilaramountof fat (assessedbyoneor twoskinfold thickness)aswesternchildrenhave,eventhoughtheirbodyweightislower58,59,leadingtotheircharacterizationas“thin-fat”.ThisrelativelygreateradiposityofIndianchildrenisof interest inviewof thepossibleeffectsof foetalprogrammingthatcouldoccurinlaterlife.FollowupstudiesofIndianchildrenhavesuggestedthatskinfoldthickness track into early childhood60. The adiposityof infants in relation to their body weight, given the“thin-fat”phenotype,anditstrackingintolaterlife,isimportanttocharacterizewhenconsideringinitiativesto reduce LBW, since increasing birth weight could beassociatedwithagreaterdegreeofadiposity.Theimplicit association that can be derived is that ofincreased body fat at birth, tracking into adulthooddepending on environmental constraints. Increasingbirthweightinsuchbabiesmightalsoimplythat theaccumulation of fat may be disproportionately moreas birth weight increases. This is not unlikely, asadult Indian populations have been shown to have ahigherpercentbodyfatforagivenBMI,thanwesternpopulations61,62, and it is worth assessing if a similarsteeperslopeintheadiposity-birthweightrelationshipis present in Indian babies. This is possible if oneconsiderstheuseofsurrogatesofadipositysuchastherelationship between the measured skinfolds or armfat index (AFI), and body weight. The relationshipbetweenskinfoldandbirthweightinBangalorebabies63can be compared with earlier studies in the UK, inSouthampton, and in India, in Pune and Mysore59,60.Using the equation derived in the Bangalore studybetweensubscapularskinfoldandbirthweight in thewholegroup,wecouldpredict themeansubscapularortricepsskinfoldforthereportedmeanbirthweightin those studies. In the UK study, the predicted andmeasuredmeansubscapular skinfoldswere identical.In contrast, for the birth weights reported in Pune59and Mysore60, the measured subscapular and tricepsskinfolds were about 0.4-0.5 mm higher than thepredictedvalue.Thereasonforthisdiscrepancyisnotclear; it is unlikely to be methodological as all sitesreportedgoodmeasurementpractices,andallexcludedmothers with gestational diabetes mellitus. It is also

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pertinenttoconsiderthatthedifferenceintheskinfoldvaluebetweenallthesereportsisabout10-15percent,whichmightsimplybeaccountedforbymeasurementerror(inter-andintra-measurererrorscanapproach1to1.5mminadults64andcouldbegreaterinthemorehydratedtissueofinfants).

Effect of daily physical activity

An important additional effect on birth weightcouldbedailyphysicalactivitywhichisanimportantand variable factor in the antenatal period, sincewomen have variable physical activities at workoutsidethehouseandwithdomestichouseholdchores.Theimportanceofthisishighlightedinstudieswhichhavedemonstratedthatmanualphysicalactivityduringpregnancy is associated with small for gestation age(SGA)babies65andlowerbirthweightsandpregnancyweight gain, particularly when energy intake is sub-optimal66. Similarly, strenuous physical work duringpregnancy has also been associated with increasedrates of abortion and premature delivery67. Increasedhouseholdchoreshavebeenrelatedtopretermbirth68,while the evidence for leisure time physical activitysuggests that participation in moderate to vigorousactivity throughout pregnancy may enhance birthweight, with more severe physical activity regimensresulting in the opposite effect69. In India, studieshave demonstrated an inverse relationship betweendailyphysicalactivityandbirthweightinacohortofruralwomen,themajorityofwhomhadhighlevelsofphysical activity related to agricultural and domesticactivities70.IndevelopingcountrieslikeIndia,womenare responsible for a wide range of household workandchildcareduties,aswellasworkoutsidethehome.Thesewomenarealsothewomenathighestriskforapoorbirthoutcome65.

Physical activity can be assessed through anintegratedindexsuchasphysicalactivitylevel(PAL),assessed through the administration of a physicalactivityrecallquestionnaire,or,throughtheassessmentof the time spent in, and the intensity of, differentactivities in the domains of work, domestic chores,transport, leisureandsleep.Therelationshipbetweenphysicalactivityandbirthweightmightbeexpectedtooperate through the maternal weight either at the first trimester,orintermsofgestationalweightgain,sincethesevariablesareassociatedwithbirthweight71.Inthisframework, relationships might be expected betweenphysical activity and maternal weight or gestationalweight gain; in sequence, these anthropometric

variables might have a subsequent relationship withbirth weight, and finally, a direct relationship between maternal physical activity and birth weight mightalso be demonstrated. If this latter relationship wasadjustedformaternalweight,itsuggeststhatmaternalphysical activity has a direct association with birthweight,independentofitseffectsonmaternalweightgain. South Indian women who had moderate/heavyphysicalactivityinthe1sttrimesterofpregnancyhada significantly higher odds of giving birth to lower birthweight babies as compared towomenwhohadsedentary physical activity (unpublished findings). ThiswasalsoinagreementwithastudyinEthiopiainwhich women were compared between categories ofhardandlightworkduringpregnancy66.

Afewstudieshaveshownassociationofworkinthethirdtrimesterandpretermbirthsandlowbirthweight.In one study, a 150-400 g decrease in birth weightoccurredinwomenwhocontinuedtoworkoutsidethehomeduring the third trimestercomparedwith thosewhoremainedathomeduringpregnancy72.Asimilardecreaseof181ginbirthweightforbabiesofwomenwhoworkedinaheavymodeoutsidethehomeduringthethirdtrimesterwasobservedbyus71.ReportsfromAfricashowthathardphysicalworkbywomenduringpregnancycanretardfoetalgrowthandincreasefoetal/neonatal mortality66,73. Indeed, the detrimental effectof third trimester work upon birth weight has beenreportedtobeexacerbatedifpregnantwomenworkedinastandingposition,werehypertensive,werepoorlynourished,orhadotheryoungchildrenathome66.

In summary, there appear to be several maternalnutritional variables that seem to be operating inassociation with low birth weight and IUGR indeveloping country women during pregnancy. While socio-economicstatusisonesuch,andmayindeedbeanissuethatunderpinsmanyoftheotheraetiologicalfactors, it also seems that maternal weight gain isimportant, in addition to specific nutrients such as vitaminB12,folateandessentialfattyacids,particularlyn-3LCPUFA.Theanalysisof theclusteringof theserisk factors in specific socio-economic or home circumstances, or in specific cultural behaviours, or in foodintakepatternsisofinterest,assuchanalysesmayprovidethewayforwardforeffectiveandsustainablepreventionstrategies.

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Reprint requests:DrSumithraMuthayya,DivisionofNutrition,St.John’sMedicalCollege&ResearchInstitute,St.John’sNationalAcademyofHealthSciences,Bangalore560034,India

e-mail:sumithra@sjri.res.in

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