Infant and Maternal Mortality in the US:Data from the National Vital Statistics System

Marian MacDorman Ph.D., Donna Hoyert Ph.D., and T.J. Mathews M.S.

Division of Vital StatisticsNational Center for Health Statistics

Centers for Disease Control and Prevention

Outline• About the data• Fetal mortality (stillbirth)• Infant mortality

– Trends, selected variables, cause of death– Relationship to preterm birth– Race and ethnic differences– International comparisons

• Maternal mortality

National Vital Statistics System• Based on birth certificates, death certificates, and

reports of fetal death filed in state vital statistics offices, and transmitted to NCHS.

• National data files produced: – Birth (natality) data set– Main mortality file– Linked birth/infant death data set

• Links birth and death certificate data for all infant deaths.• Purpose: To use more detailed data from the birth certificate for

infant mortality analysis.

– Fetal death data reported by all US states • Most states report fetal deaths of 20 weeks of gestation or more.• Some variability in data completeness and quality.

National Vital Statistics System – Analytical Challenges

• Certificate revision in 2003, but not all states have adopted

• Some items not comparable between old and new versions of the certificates

• Timeliness of data file availability is highly variable– Preliminary birth and death certificate data now available

through 2009– Linked birth/infant death data through 2007– Fetal death data through 2005

• NCHS is working to catch up on data production in a limited resource climate.

Fetal Mortality

All pregnancies, US, 2005(n=6.4 million pregnancies)

65%

17%

19%

Source: Ventura SJ, Abma JC, Mosher WD. Estimated pregnancy rates for the United States, 1990-2005: An Update. National vital statistics reports vol 58 no 4. 2009.

1.2 millioninduced terminations

1.1 millionfetal deaths

4.1 million live births

(28,384)

(25,894)

Fetal mortality rate 1990-2005, and infant mortality rate, 1990-2009

5

6

7

8

9

10

1990 1995 2000 2005 2009

Rate

per

1,00

0

0

Infant

Fetal

NOTE: Infant mortality rates are the number of infant deaths per 1,000 live births. 2007 data are preliminary. Fetal mortality rates are the number of fetal deaths of 20 weeks of gestation or more per 1,000 live births and fetal deaths. SOURCE: CDC/NCHS, National Vital Statistics System.

Fetal mortality rates by period of gestation: US, 1990-2005

2

3

4

5

1990 1995 2000 2005

Rate

per 1

,000 l

ive b

irths

and

fetal

death

s in

spec

ified

gro

up

28 weeks or more

20-27 weeks

SOURCE: MacDorman MF and Kirmeyer S. Fetal and perinatal mortality, US, 2005. National vital statisticsreports vol 57 no 8.

0

Fetal mortality rates by race and Hispanic origin of mother: US, 2005

3.21 2.36

6.40

2.83 2.49 2.63

3.032.45

4.80

3.352.30 2.82

6.22

4.79

6.17

4.785.44

0

2

4

6

8

10

12

14

Total Non-Hispanicwhite

Non-Hispanicblack

AmericanIndian

Asian orPacific

Islander

Hispanic

Rate

per 1

,000

live

births

and

fetal

death

s in s

pecif

ied g

roup Fetal 20-27 weeks Fetal 28 weeks or more

NOTE: Rates for subtotals do not add exactly to totals due to slight differences in the denominators used for rate computations; see Technical notes.SOURCE: Fetal and perinatal mortality, US, 2005. National vital statistics reports vol 57 no 8.

11.13

Prospective fetal mortality rate by single weeks of gestation: US, 2005

00.10.20.30.40.50.60.70.80.9

20 22 24 26 28 30 32 34 36 38 40 42Gestational age

Note: The prospective fetal mortality rate is the number of fetal deaths at a given gestational age per 1,000 live births and fetal deaths at that gestational age or greater.

Source: MacDorman MF, Kirmeyer S. Fetal and perinatal mortality, US, 2005. National vital statistics reports vol 57 no 8.

43

Infant Mortality:Trends and selected variables

Infant mortality rate, United States, 2000-2009

6.89 6.84 6.95 6.84 6.78 6.86 6.68 6.75 6.59 6.42

0

2

4

6

8

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Rat

e pe

r 1,0

00 li

ve b

irths

Source: 2000-2007 data are from the linked birth/infant death data sets. 2008 and 2009 data are preliminary data from the main mortality files.

8.74

4.55 5.14 4.42 3.61 3.68 3.65 3.38 3.14

4.57

4.672.57

2.332.02 1.75 1.53 1.4 1.43

0

2

4

6

8

10

12

14

Non-Hispanicblack

AmericanIndian

Puerto Rican TOTAL Non-Hispanicwhite

Mexican Cuban Asian orPacific

Islander

Central andSouth

American

Infa

nt m

orta

lity

rate

per

1,0

00 li

ve b

irths

Neonatal Postneonatal13.31

9.22

7.716.75

5.63 5.42 4.78 4.575.18

Infant mortality rates by maternal race and ethnicity, 2007

Source: NCHS linked birth/infant death data set, 2007

13.55

7.6 7.156.32 6.11 5.66

4.79 4.80

9.82

7.73

5.14.25

4.964.14

5.334.52

0

5

10

15

Non-Hispanicblack

Puerto Rican Total Asian orPacific

Islander

Mexican Non-Hispanicwhite

Cuban Central andSouth

American

Rat

e pe

r 1,0

00 li

ve b

irths

Born in the U.S. Born elsewhere

Infant mortality rates by mother’s place of birth and race/ethnicity, 2007

Source: NCHS, linked birth/infant death data set, 2007

Infant mortality rates by maternal age, US, 2007

6.75

14.53

9.73

7.67

5.97 5.37 6.20

8.35

11.70

0

5

10

15

20

Total <15 15-19 20-24 25-29 30-34 35-39 40-44 45+

Rat

e pe

r 1,0

00 li

ve b

irths

Source: NCHS, linked birth/infant death data set, 2007.

Infant mortality rates by plurality, 2007

6.75 5.9328.39

64.69

140.92

296.70

0

50

100

150

200

250

300

350

Total Single Twin Triplet Quadruplet 5+

Rat

e pe

r 1,0

00 li

ve b

irths

Source: CDC/NCHS linked birth/infant death data set, 2007

Infant mortality rates by selected variables: 19 states, 2007

<HS HS Some BA/BScollege

Nonsmoker Smoker1st After 1st

Source: NCHS, linked birth/infant death data set

7.78

5.57 6.107.17

7.94

10.41

5.79

3.77

0

5

10

15

Trimester prenatal care began Maternal Smoking Maternal Education

Infa

nt d

eath

s pe

r 1,0

00 li

ve b

irths

+

Infant mortality rates by leading causes of death, US, 2000 and 2007

141.8

108.4

62.1

34.321.6

134.9

112.7

5741.1

29.7

0

20

40

60

80

100

120

140

160

Congenitalmalformations

Short gest/LBW SIDS Maternalcompl.

Unintentionalinjuries

Rat

e pe

r 100

,000

live

birt

hs

2000 2007

Source: NCHS, linked birth/infant death data set.

Percentage of Infant Deaths from Preterm-Related Causes* by Race/Ethnicity, US, 2000 and 2007

43.739.6

34.632.3 30.5 30.8 29.4 27.7

45.0

39.436.0 34.6 35.4

31.6 32.6

24.3

0

5

10

15

20

25

30

35

40

45

50

Non-Hispanicblack

Puerto Rican TOTAL Central andSouth

American

Asian orPacific

Islander/1

Non-Hispanicwhite

Mexican AmericanIndian orAlaskanative/1

Per

cent

2000 2007

* Infants born at <37 weeks of gestation with cause of death that was a direct cause or consequence of preterm birth (ICD-10 codes K550, P000, P010, P011, P015, P020, P021, P027, P070-P073, P102, P220-P229, P250-279, P280, P281, P360-P369, P520-P523, P77).1/ Includes persons of Hispanic and non-Hispanic origin.SOURCE: NCHS, linked birth/infant death data set.

13.31

9.22

7.716.75

5.63 5.424.78 4.57

5.99

2.253.04

2.431.78 1.77 1.69 1.58

0

5

10

15

Non-Hispanic

black

AmericanIndian orAlaskanative^

Puerto Rican Total Non-Hispanic

white

Mexican Asian orPacific

Islander^

Central andSouth

American

Rat

e pe

r 1,0

00 li

ve b

irths

Total Preterm-related

Total and preterm-related* infant mortality rates by race and ethnicity of mother, US, 2007

* Preterm-related deaths are those where the infant was born preterm with the underlying cause of death assigned to one of the following ICD-10 categories: K550, P000, P010, P011, P015, P020, P021, P027, P070-P073, P102, P220-P229, P250-279, P280, P281, P360-P369, P520-P523, P77.^Includes persons of Hispanic and Non-Hispanic origin. SOURCE: NCHS linked birth/infant death data set, 2007

Infant Mortality and Preterm Birth

Infant mortality rates by gestational age ( in weeks), US, 2007

6.75

178.36

16.127.42 3.09 2.07 2.62

020406080

100120140160180200

Total <32 32-33 34-36 37-38 39-41 42+

Rat

e pe

r 1,0

00 li

ve b

irths

Source: NCHS, linked birth/infant death data set.

Percent of live births and infant deaths by weeks of gestation, US, 2007

<3254%

32-334%

34-3610%

37+32%

Infant Deaths<322% 32-33

2% 34-369%

37+87%

Births

Source: NCHS, linked birth/infant death data set

Components of preterm birth

“Indicated” preterm birth30-35%

PROM 25-30%

Spontaneous preterm labor40-45%

Source: Goldenberg et al. Lancet, 2008.

Percentage of preterm births: US, selected years

3.13 3.32 3.31 3.42 3.63 3.66 3.64 3.56 3.51

6.37.3 7.7 8.2

9.1 9.1 9.0 8.8 8.7

0

2

4

6

8

10

12

14

1984 1990 1995 2000 2005 2007 2009

Per

cent

pre

term

12.7 12.8 12.7 12.3 12.2

10.611.0

11.6

9.4

Source: CDC/NCHS national natality files. 1984-2008 are final birth data, 2009 data are preliminary.

34-36 weeks:↑44% 1984-2006↓4% 2006-2009

<34 weeks: ↑ 17% 1984-2006↓ 4% 2006-2009

Percent of preterm births by race and ethnicity, US, 1990 and 2006-2009

10.6

8.5

18.9

11.012.8

11.7

18.5

12.212.210.9

17.5

12.0

0

2

4

6

8

10

12

14

16

18

20

Total Non-Hispanicwhite

Non-Hispanicblack

Hispanic1990 2006 2007 2008 2009 1990 2006 2007 2008 2009 1990 2006 2007 2008 2009 1990 2006 2007 2008 2009

Source: CDC/NCHS national natality files. 1990-2008 data are final. 2009 data are preliminary.

Percent of singleton births delivered by cesarean by gestational age, US, selected years

2125

3128

2329

37

4742

34

05

101520253035404550

37+ weeks <37 weeks <32weeks

32-33weeks

34-36weeks

Perc

ent

1991199620012006

Source: MacDorman et al, AJPH, 2010.

Percent of singleton births with induction of labor, US, selected years

118

57 8

24

16

9

13

17

0

5

10

15

20

25

30

37+ weeks <37 weeks <32weeks

32-33weeks

34-36weeks

Perc

ent

1991199620012006

Source: MacDorman et al, AJPH, 2010.

Percent of singleton preterm (<37 weeks) births by method of delivery, US, 1991-2006

0

2

4

6

8

10

12

1991 1996 2001 2006

Perc

ent

Cesarean noinduction

Cesarean afterinduction attempt

Induced vaginal

Spontaneousvaginal

Note: Births with method of delivery and induction of labor not stated are excluded. Source: MacDorman et al, AJPH, 2010.

Infant Mortality:Race and ethnic differences

13.31

9.22

7.716.75

5.63 5.42 5.18 4.78 4.57

0

2

4

6

8

10

12

14

Non-Hispanicblack

AmericanIndian

Puerto Rican Total Non-Hispanicwhite

Mexican Cuban Asian orPacific

Islander

Central andSouth

American

Infa

nt m

orta

lity

rate

per

1,0

00 li

ve b

irths

Figure 1. Infant mortality rates by race and ethnicity of mother, US, 2007

Source: CDC/NCHS linked birth/infant death data set, 2007.

Infant mortality can be partitioned into two key components:

1. Gestational age-specific infant mortality rates (i.e. the mortality rate for infants at a given gestational age).

2. Distribution of births by gestational age.

Gestational age-specific infant mortality rates by race/ethnicity, US, 2007

165.6

16.2

209.0

16.9

172.2157.0

28.5

0

50

100

150

200

250

<32 weeks 32-33 weeks

Rat

e pe

r 100

0 liv

e bi

rths

Non-Hispanic whiteNon-Hispanic blackPuerto RicanAmerican Indian

*

Source: CDC/NCHS linked birth/infant death data set, 2007* Figure does not meet standard of reliability or precision: based on <20 deaths in the numerator.

Gestational age-specific infant mortality rates by race/ethnicity, US, 2007

7.1

3.02.0

9.4

4.53.4

8.2

3.12.3

14.3

6.1

3.8

0

2

4

6

8

10

12

14

16

34-36 weeks 37-38 weeks 39-41 weeks

Rat

e pe

r 100

0 liv

e bi

rths

Non-Hispanic whiteNon-Hispanic blackPuerto RicanAmerican Indian

Source: CDC/NCHS, linked birth/infant death data set, 2007

0

2

4

6

8

10

12

14

16

18

20

Non-Hispanicwhite

Non-Hispanicblack

Puerto Rican AmericanIndian

moderately pretermvery preterm

18.3

11.5

14.5 13.9

Percent of preterm births by race and Hispanic origin of mother, United States, 2007

Note: Preterm: <37 weeks of gestation; very preterm: <32 weeks; moderately preterm: 32-36 weeksSource: CDC/NCHS linked birth/infant death data set, 2007

Percent contribution of gestational-age specific infant mortality rates and the distribution of births by gestational

age to race/ethnic differences in infant mortality rates

78

100

24

22

0

76

0%

20%

40%

60%

80%

100%

NHB/NHW infantmortality gap

PR/NHW infantmortality gap

AI/NHW infantmortality gap

Gestational age-specific infantmortality ratesDistribution ofbirths bygestational age

Note: NHW=non-Hispanic white, NHB=non-Hispanic black, PR=Puerto Rican, AI=American IndianSource: NCHS linked birth/infant death data set, 2007

Contribution of causes of death to the non-Hispanic black – non-Hispanic white infant mortality gap, 2007

599

165108

61

178124

58 300

100

200

300

400

500

600

Preterm-relatedcauses

Congenitalmalformations

SIDS Unintentionalinjuries

Infa

nt m

orta

lity r

ate p

er 10

0,000

live b

irths

Non-Hispanic black Non-Hispanic white

55% of difference

5% of difference

6% of difference 4% of

difference

Overall, 71% of the black-white infant mortality gap is due to these causes

Source: CDC/NCHS linked birth/infant death data set, 2007

Contribution of causes of death to the Puerto Rican -- non-Hispanic white infant mortality gap, US, 2007

304

137

58*

178

124

5830

0

50

100

150

200

250

300

350

400

Preterm-related Congenitalmalformations

SIDS Unintentionalinjuries

Infa

nt m

orta

lity

rate

per

100

,000

live

birt

hs Puerto Rican Non-Hispanic white

61% of difference

6% of difference

Source: CDC/NCHS linked birth/infant death data set, 2007. * Figure does not meet standard of reliability or precision – based on <20 deaths in the numerator.

Contribution of causes of death to the American Indian -- non-Hispanic white infant mortality gap, US, 2007

225

184

142

69

178

124

5830

0

50

100

150

200

250

300

350

400

Preterm-related Congenitalmalformations

SIDS Unintentionalinjuries

Infa

nt m

orta

lity

rate

per

100

,000

live

birt

hs American Indian Non-Hispanic white

23% of difference

17% of difference

13% of difference

11% of difference

Overall, 64% of the American Indian-white infant mortality gap is due to these causes

Source: CDC/NCHS linked birth/infant death data set, 2007.

Infant Mortality:International comparisons

Infant mortality rates, selected countries, 2005

7.26.9

6.46.3

6.26.2

5.45.2

5.15.05.0

4.94.7

4.64.4

4.24.2

4.14.0

3.93.8

3.73.6

3.53.4

3.13.0

2.82.42.4

2.1

0 1 2 3 4 5 6 7

SlovakiaUnited States

PolandNorthern Ireland

CubaHungaryCanada

ScotlandNew Zealand

AustraliaEngland and Wales

NetherlandsItaly

IsraelDenmark

AustriaSwitzerland

SpainIreland

GermanyGreece

BelgiumFrance

PortugalCzech Republic

NorwayFinland

JapanHong Kong

SwedenSingapore

Rate per 1,000 live birthsSource: Health, United States, 2008

Infant mortality rates excluding births at <22 weeks of gestation, US and selected European countries, 2004

7.06.8

6.65.8

4.94.9

4.64.6

4.44.14.1

4.04.04.04.0

3.93.9

3.73.4

3.03.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

SlovakiaPoland

HungaryUnited States

ScotlandEngland and Wales

NetherlandsIreland

DenmarkGermany

AustriaSpain

Northern IrelandItaly

GreecePortugal

FranceCzech Republic

FinlandSwedenNorway

Rate per 1,000 live births

Source: NCHS linked birth/infant death data set (for US data), and European Perinatal Health Report (for European data).

Percentage of preterm births, United States and selected European countries, 2004

12.411.4

8.98.6

8.07.67.57.4

7.17.06.96.86.86.8

6.66.36.36.3

6.05.65.5

0 2 4 6 8 10 12 14

United StatesAustria

GermanyHungary

SpainScotland

England and WalesNetherlands

NorwayCzech Republic

DenmarkItaly

PolandPortugal

Northern IrelandFrance

SlovakiaSwedenGreeceFinlandIreland

Note: Excludes births at <22 weeks of gestation to promote comparability between countries. Preterm births are those from 22 to 36 weeks of gestation. Source: NCHS linked birth/infant death data set (for US data), and European Perinatal Health Report (for European data).

Infant mortality rate for the US and Sweden, and the US infant mortality rate standardized for

Sweden’s gestational age distribution, 2004

3.0

5.8

3.9

0

1

2

3

4

5

6

7

Sweden IMR US IMR US IMR if the UShad Sweden'sgestational age

distribution

Infa

nt m

orta

lity

rate

33% lower

Note: Excludes births at <22 weeks of gestation. Source: NCHS linked birth/infant death data set (for US data), and European Perinatal Health Report (for Swedish data).

Discussion – International Rankings• Although there are reporting differences between countries,

they are not the primary explanation for the United States’ relatively low international ranking.

• In 2005, 22 countries had infant mortality rates ≤5.0.

• One would have to assume that these countries did not report more than 1/3 of their infant deaths for their infant mortality rates to equal or exceed the US rate.

• This level of underreporting appears unlikely for most developed countries.

• The main cause of the US’ high infant mortality rate when compared to Europe is the very high percentage of preterm births in the US, the period when infant mortality is greatest.

Maternal Mortality:What’s the real story?

DefinitionsMaternal death: Death of a woman while pregnant or within 42 days of the end of pregnancy from any cause related to or aggravated by the pregnancy.

Late maternal death: Death of a woman from direct or indirect obstetric causes more than 42 days but less than one year after the end of the pregnancy.

Maternal mortality rate: Number of maternal deaths x 100,000(also known as maternal mortality ratio) Number of live births

Source: World Health Organization, International Classification of Diseases, 10th Revision.

Two Main Maternal Mortality Data Systems

National Vital Statistics System (NVSS):• Official maternal mortality rate for US• Based upon death certificates• Maternal deaths, late maternal deaths, sequelae of maternal death• Coded according to WHO rules

Pregnancy Mortality Surveillance System (PMSS):• Complementary activity to NVSS• Based upon death certificates, matched records, media reports, maternal mortality review committee reports etc.• Pregnancy-related deaths, pregnancy associated deaths• Reviewed and coded according to system developed by ACOG/CDC Maternal Mortality Study Group

Maternal mortality rates from the National Vital Statistics System and the Pregnancy Mortality Surveillance System, US, 1980-2002

0

2

4

6

8

10

12

14

16

18

1980 1985 1990 1995 2000 2005

Rate

per

100

,000

live

birt

hs

PMSS

NVSS

Source: CDC/NCHS National Vital Statistics System, and CDC Pregnancy Mortality Surveillance System.

Recent change involving separate question

• Beginning with data for 2003, states have been adopting a separate question on their death certificates on whether a woman was pregnant at the time of death or within 42 days of death.

• Information from the question is used to supplement what is reported on the cause-of-death statement to improve ascertainment of maternal deaths

•The new question increases ascertainment of maternal deaths leading to higher maternal mortality rates.

Number of states with pregnancy question on the death certificate, 2003-2011

412

18 22 2431 31 35 38

05

101520253035404550

2003 2004 2005 2006 2007 2008 2009 2010 2011

Standard questionAnother questionNo question

Source: CDC/NCHS National Vital Statistics System.

Maternal mortality rates from the National Vital Statistics System and the Pregnancy Mortality Surveillance System, US, 1980-2007

0

2

4

6

8

10

12

14

16

18

1980 1985 1990 1995 2000 2005 2007

Rate

per

100

,000

live

birt

hs PMSS

NVSS

Source: CDC/NCHS National Vital Statistics System, and CDC Pregnancy Mortality Surveillance System.

Maternal Mortality is Still a Major Public Health Problem

• Maternal mortality rates in the US are high compared to other industrialized countries.

• No improvement in maternal mortality rates in the US since the 1980’s

• 500-600 maternal deaths each year in the United States

• Unexpected deaths of young women many in their 20s and 30s, many with families and other children

• There are large race and ethnic disparities in maternal mortality –some of the widest disparities found in public health.

• At least 40% of pregnancy-related deaths are preventable (Berg, 2005). Many due to common problems such as hemorrhage or complications of maternal chronic diseases (i.e. diabetes, hypertension).

Maternal mortality rates, selected industrialized countries, 2003-2004 data

12.6

9.3

8.8

7.2

7.0

6.2

5.4

0 2 4 6 8 10 12 14

United States

Denmark

Netherlands

England and Wales

France

Canada

Germany

Source: European data from the European Perinatal Health Report; Canadian data from Statistics Canada, Canadian vital statistics, death database; US data from the National Vital Statistics System.

Maternal mortality rates by race and Hispanic origin, US, 2007

Total Hispanic Non-Hispanic white

Non-Hispanic black

0

5

10

15

20

25

30

35

Rat

e pe

r 100

,000

live

birt

hs

12.7

8.9 10.5

28.4

Source: CDC/NCHS, National Vital Statistics System, Mortality

Maternal mortality rates by age, US, 2007

7.1 8.1 9.412.1

32.3

0

5

10

15

20

25

30

35

Under 20 20-24 25-29 30-34 35 and over

Rat

e pe

r 100

,000

live

birt

hs

Age in years

Source: CDC/NCHS National Vital Statistics System, Mortality

Summary• Stagnation in the rate of decline of both infant

(2000-2007) and fetal (2003-2005) mortality rates

• No detectible decline in maternal mortality rate since 1982

• Recent modest decline in preterm birth (2006-9) and infant mortality (2007-9)

• Still, preterm birth rates and infant mortality rates are much higher in the US than in most developed countries.

Summary (cont.)• Large race and ethnic disparities in fetal, infant and

maternal mortality suggest that not all race/ethnic groups have benefited equally from social and medical advances.

• Preterm birth is a primary cause of high infant mortality in the US, and contributes substantially to both race and ethnic disparities and the US’ poor international ranking.

• Interventions to address the nation’s high preterm birth rate must address prevention of both spontaneous preterm labor and iatrogenic preterm birth.

Questions?

Marian MacDorman, Ph.D.Statistician, Division of Vital StatisticsNational Center for Health Statistics(301) 458-4356mfm1@cdc.gov

2007 linked file report available at : http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_06.pdfSome copies in the back of the room.