Recent Declines in Infant Mortality in the United States

Marian MacDorman, PhD and T.J. Mathews, MSDivision of Vital Statistics

National Center for Health Statistics

Vital Statistics Infant Mortality Data

• Based on birth and death certificates filed in state vital statistics offices, and transmitted to NCHS.

• National data files produced:

– Birth (natality) data set – 2011 preliminary and 2010 final currently available

– Main mortality file – 2011 preliminary and 2010 final currently available

– 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.

• Currently available through 2008; 2009 expected by Jan. 2013

2000 2002 2004 2006 2008 2010 20110

1

2

3

4

5

6

7

8

4.62 4.54 4.67 4.63 4.52 4.54 4.46 4.42 4.29 4.18 4.05 4.04

2.27 2.30 2.28 2.22 2.25 2.32 2.22 2.33 2.32 2.21 2.10 2.01

Neonatal Postneonatal

Rate

per

1,0

00 li

ve b

irths

6.89 6.84

6.056.39

6.15

6.68 6.75 6.84 6.78 6.866.61

6.95

Infant, neonatal and postneonatal mortality rates, United States, 2000-2011

Source: NCHS linked birth/infant death data set, 2000-2009, mortality data set 2010, and preliminary mortality data set, 2011.

Percentage of preterm births: United States, 2000-2011

2000 2002 2004 2006 2008 2010 20110

2

4

6

8

10

12

14

3.4 3.4 3.5 3.5 3.6 3.6 3.7 3.6 3.6 3.5 3.5 3.4

8.1 8.4 8.6 8.8 8.9 9.1 9.1 9 8.8 8.66 8.49 8.3

<34 weeks 34-36 weeks

Per

cent

pre

term

12.3 12.211.6

12.3 12.5 12.7 12.8 12.711.6 11.9 12.1

Source: Births: Final data for 2010; Births, preliminary data for 2011.

11.9

Percent distribution of births by gestational age, US, 2006 and 2010

<34 34-36 37-38 39-41 42+0

10

20

30

40

50

60

70

3.79.1

28.9

52.6

5.73.5

8.5

26.9

55.6

5.7

2006 2010

Pe

rce

nt

SOURCE: National Vital Statistics System, NCHS, CDC.

Completed weeks of gestation

Infant mortality rate and percent of preterm births, US, 2000-2011

2000 2002 2004 2006 2008 2010 20110

1

2

3

4

5

6

7

8

0

2

4

6

8

10

12

6.89 6.84 6.95 6.84 6.78 6.86 6.68 6.75 6.61 6.39 6.15 6.05

Infant mortality rate % preterm

Infa

nt m

ort

alit

y ra

te p

er

1,0

00

live

birt

hs

Per

cen

t of

pre

term

bir

ths

Source: CDC/NCHS; national vital statistics system

Infant mortality rates by gestational age, US, 2008

Total <32 32-33 34-36 37-38 39-41 42+ 0

20

40

60

80

100

120

140

160

180

200

6.61

175.45

17.587.40 3.13 2.08 2.69

Ra

te p

er

1,0

00

live

birt

hs

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

Completed weeks of gestation

Percent of births and infant deaths by gestational age (weeks), US, 2008

<32Se-

ries153%

32-33Series1

4%

34-36Se-

ries110%

37+Se-

ries133%

Infant DeathsBirths 34-36

9%

37+87%

<322%

32-332%

Source: CDC/NCHS Linked birth/infant death data set, 2008

Components of infant mortalityThe overall infant mortality rate can be partitioned into two key components:

1. The distribution of births by gestational age;

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

Component 1 available through 2011; component 2 through 2008

Preliminary modeling suggests that both must have declined to yield the current infant mortality rate

Race/Ethnic Differences

0

2

4

6

8

10

12

1412.67

8.42

7.296.61

5.58 5.524.9 4.76 4.51

Ra

te p

er

1,0

00

live

bir

ths

Infant mortality rates by maternal race/ethnicity, US, 2008

Source: CDC/NCHS linked birth/infant death data set, 2008.

Non- American Puerto Total Mexican Non- Cuban Central Asian orHispanic Indian Rican Hispanic or South Pacific black white American Islander

Percent contribution of two components to race and ethnic differences in infant mortality rates, 2007

NHB/NHW infant mortality gap

PR/NHW infant mortality gap

AI/NHW infant mortality gap

0%

20%

40%

60%

80%

100%

78

100

24

22

0

76

Gestational age-specific infant mor-tality ratesDistribution of births by gestational age

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

Infant mortality rates by race/ethnicity, US, 2000, 2005 and 2011

Total Non-Hispanic white

Non-Hispanic black

Hispanic0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

6.915.71

14.11

5.646.87

5.73

14.28

5.806.055.05

11.96

5.27

2000 2005 2011

Source: Data from the vital statistics mortality file. Note: Infant mortality rates by race and Hispanic origin are more accurate from the linked birth/infant death data set.

Percent of preterm births by maternal race/ethnicity, US, 2000, 2006, 2011

Total Non-Hispanic white

non-Hispanic black Hispanic0

2

4

6

8

10

12

14

16

18

20

11.610.4

17.4

11.2

12.811.7

18.5

12.211.710.5

16.8

11.7

2000 2006 2011

Trends in Leading Causes

Of Infant Death

Infant mortality rates for the five leading causes of infant death in 2011: US, 2000, 2005, and 2011

0

20

40

60

80

100

120

140

160141.5

108.3

62.2

34.6

21.7

134.2

113.9

53.942.9

26.2

126.1

104.1

43.3 39.9

27.5

2000 2005 2011

Rate

per

100

,000

live

birt

hs

Source: NCHS, mortality data set. 2011 data are ore preliminary.

State Differences

MT

WY

ID

WA

OR

NV

UT

CA

AZ

ND

SD

NE

CO

NM

TX

OK

KS

AR

LA

MO

IA

MN

WI

IL IN

KY

TN

MS AL GA

FL

SC

NC

VAWV

OH

MI

NY

PA

MD

DE

NJ

CT RI

MA

ME

VT

NH

AK

HI

DC

Infant mortality rates by State, 2010

Source: National Vital Statistics System, NCHS, CDC

5.00 to 5.99

Less than 5.00

6.00 to 6.99

7.00 to 7.99

More than 8.00

U.S. rate = 6.15

MT

WY

ID

WA

OR

NV

UT

CA

AZ

ND

SD

NE

CO

NM

TX

OK

KS

AR

LA

MO

IA

MN

WI

IL IN

KY

TN

MS AL GA

FL

SC

NC

VAWV

OH

MI

NY

PA

MD

DE

NJ

CT RI

MA

ME

VT

NH

AK

HI

DC

Decline in infant mortality rates by state, 2005-2010

Source: National Vital Statistics System, NCHS, CDC

No significant change

Statistically significant decline of <20%

Statistically significant decline of 20% or more

U.S. change = -10.5

Understanding the Recent Decline in Preterm Birth

Understanding the Recent Decline in Preterm Birth

Decline in preterm births from 2006-2010 appears to be widespread. Declines in preterm rates for most/all: - maternal race/ethnic groups - maternal age groups - states - among both single and multiple births

Some factors to consider in changes to overall rate: - Recent decline in teen births (who have higher preterm rates)- Leveling out of multiple birth rates- Changes in obstetrical management of pregnancy

Components of preterm birth

“Indicated” preterm birth30-35%

PROM 25-30%

Spontaneous preterm labor40-45%

Source: Goldenberg et al. Lancet, 2008.

Percent preterm for cesarean, induced vaginal, and non-induced vaginal births: US, 2000, 2006, and 2010

Cesarean births Induced Noninduced0

2

4

6

8

10

12

14

16

18

20

17.1

7.7

10.6

17.8

7.7

11.6

16.7

6.8

10.7

2000 2006 2010

Vaginal births

International Comparisons

Infant mortality rates, OECD countries, 2009

United StatesSlovak Republic

PolandNew Zealand

HungaryUnited Kingdom

AustraliaSwitzerland

FranceItaly

AustriaIsrael

NetherlandsPortugal

GermanyBelgium

IrelandRepublic of Korea

SpainDenmark

GreeceNorway

Czech RepublicFinlandSweden

JapanIceland

0 1 2 3 4 5 6 7

6.45.7

5.65.2

5.14.6

4.34.3

3.93.9

3.83.83.8

3.63.5

3.43.23.23.2

3.13.13.1

2.92.6

2.52.4

1.8

Rate per 1,000 live birthsSource: Health, United States, 2012. OECD=Organization for Economic Cooperation and Development.

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

United StatesAustria

GermanyHungary

SpainScotland

England and WalesNetherlands

NorwayCzech Republic

DenmarkItaly

PolandPortugal

Northern IrelandFrance

SlovakiaSwedenGreeceFinlandIreland

0 2 4 6 8 10 12 14

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

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).

Conclusions- After a plateau from 2000-2005, the US infant mortality rate

declined 12% from 2005 to 2011.

- After more than two decades of increase, there was a 9% decrease in the preterm birth rate from 2006-2011.

- From 2005-2011, infant mortality declined most rapidly for non-Hispanic black women (-16%), followed by non-Hispanic white (-12%) and Hispanic women (-9%), based on mortality file data.

- Infant mortality declines were largest for states such as Louisiana, Georgia, the Carolinas and DC with large African-American populations and which previously had persistently high infant mortality rates.

- Provisional data from July 2011-June 2012 show a US infant mortality rate of 5.9, suggesting a continued downward trend from the rate of 6.05 in 2011.

Links to some recent reports

Infant mortality statistics from the 2008 linked birth/infant death data set: http://www.cdc.gov/nchs/data/nvsr/nvsr60/nvsr60_05.pdf

Deaths, preliminary data for 2011: http://www.cdc.gov/nchs/data/nvsr/nvsr61/nvsr61_06.pdf

Tables from Deaths, Final data for 2010:http://www.cdc.gov/nchs/data/dvs/deaths_2010_release.pdf

Births, preliminary data for 2011: http://www.cdc.gov/nchs/data/nvsr/nvsr61/nvsr61_05.pdf

Births: final data for 2010:http://www.cdc.gov/nchs/data/nvsr/nvsr61/nvsr61_01.pdf

Provisional monthly and 12 month ending number of deaths, live births and infant deaths and rates: United States, January 2011 to June 2012. http://www.cdc.gov/nchs/data/dvs/provisional_tables/Provisional_Table01_2012Jun.pdf

Contact information

Marian MacDorman 301-458-4356 mfm1@cdc.gov

T.J. Mathews301-458-4363tjm4@cdc.gov

Any questions?