Transcript The Early Childhood Longitudinal Study – Birth Cohort (ECLS-B)

Explaining the 2001-02 Infant
Mortality Increase
Marian MacDorman, Joyce Martin, T.J.Mathews,
Donna Hoyert, and Stephanie Ventura
Division of Vital Statistics
National Center for Health Statistics
Centers for Disease Control and Prevention
Infant Mortality Rate:
United States, 1990-2002
Deaths under 1 year per 1,000 live births
10
9
8
+3%
7
6
50
1990
1992
1994
1996
1998
SOURCE: National Vital Statistics System, NCHS, CDC.
2000
2002
Infant Deaths and Infant, Neonatal, and
Postneonatal Mortality Rates: US, 2001-02
[Rates per 1,000 live births]
Infant mortality rate
Neonatal (Under 28 days)
Year
Infant
deaths
Total
Total
Under 7
days
7-27
days
Postneonatal
(28 days –
11 months)
2002
27,970
7.0
4.7
3.7
0.9
2.3
2001
27,523
6.8
4.5
3.6
0.9
2.3
SOURCE: National Vital Statistics System, NCHS, CDC.
Infant Mortality Rates by Maternal Race and
Ethnicity: United States, 2001 and 2002
15
2001
Rate per 1,000 live births
13.5
13.9
2002
10
9.7
8.6
5.7 5.8
5
5.4 5.6
4.7 4.8
0
Non-Hispanic
black
American
Indian
Non-Hispanic
white
SOURCE: National Vital Statistics System, NCHS, CDC
Hispanic
Asian or Pacific
Islander
Infant Mortality Rates by Leading
Causes: United States, 2001-02
[Rates per 100,000 live births]
Cause of death (ICD-10)
2002
2001
Congenital anomalies
144.0
137.6
Short gestation/low birthweight
115.3
109.5
Sudden infant death syndrome
57.1
55.5
Maternal complications of pregnancy
42.4
37.3
NOTE: Bold, underlined numbers indicate a statistically significant increase from the previous year.
SOURCE: National Vital Statistics System, NCHS, CDC.
Infant Mortality Rates by
Birthweight: United States, 2002
1000
Per 1,000 live births
900
862.0
800
700
600
500
489.6
400
300
200
155.1
100
0
<500
70.3
500749
750999
10001249
45.7
12501499
grams
SOURCE: National Vital Statistics System, NCHS, CDC.
26.5
15001999
11.5
20002499
2.4
2500+
Percent of Births and Infant Deaths
by Birthweight, United States, 2002
100
Births
80
Infant deaths
92.2
53.9
60
40
32.0
14.0
20
1.5
6.4
0
<1500
1500-2499
Birthweight in grams
SOURCE: National Vital Statistics System, NCHS, CDC
2500+
Components of Infant Mortality
• The distribution of births by birthweight.
• Birthweight-specific infant mortality rates
(the mortality rate for infants at a given
weight)
Number of Live Births at <750 grams,
United States, 2001 and 2002
20000
18000
16000
+3%
2001
2002
17531
14000
+2%
12000
11081
10000
8000
6000
18070
11290
+5%
6450
6780
4000
2000
0
<500
500-749
Birthweight in grams
SOURCE: National Vital Statistics System, NCHS, CDC
<750
Infant Mortality Rates by Birthweight,
United States, 2001 and 2002
300
250
244.4 250.8
2001
2002
200
150
100
50
15.2 15.1
2.4
2.4
0
<1500
1500-2499
Birthweight in grams
SOURCE: National Vital Statistics System, NCHS, CDC
2500+
Direct Standardization
Used to measure the proportion of the overall 20012002 infant mortality increase due to a change in:
- The distribution of births by birthweight (98%)
- Birthweight-specific infant mortality rates (2%)
Results by Period of Gestation
• Increase in the number and percent of extremely
preterm births (<28 weeks)
• Significant increase in infant mortality rates for
preterm (<37 weeks) and very preterm (<32 weeks)
• Direct Standardization indicated that:
• 61% of the increase was due to a change in the
distribution of births by gestational age.
• 39% due to a change in gestational age-specific infant
mortality rates.
Contribution of Multiple Births to 2001-02
Infant Mortality Increase
• Number of multiple births increased by:
- 3% overall
- 4% for <750 gram births
• Changes for multiple births accounted for ¼ of the
overall infant mortality increase
• ¾ was due to changes for single births
Possible Factors that Might Explain the
Increase in <750 Gram Births
• Changes in reporting of births and/or fetal
deaths.
• Changes in the risk profile of births.
• Changes in medical management of
pregnancy.
The Potential Influence of
Reporting Changes
Percent of Live Births and Fetal Deaths
20+ Weeks, by Birthweight: US, 2001-02
Live Births
Fetal deaths 20+ weeks
60.0
.50
.45
0.419
0.432
.40
.35
.30
0.271
48.6
50.0
47.8
40.0
15.0
14.6
32.8
34.0
2001
2002
0.276
.25
30.0
.20
20.0
.15
.10
.05
0.148
10.0
0.156
.00
0.0
2001
2002
<500 g
500-749 g
SOURCE: National Vital Statistics System, NCHS, CDC
Percent of Fetal Deaths 20+ Weeks that Occur at
20-27 Weeks: States Reporting All Periods of
Gestation and All Other States, Selected Years
70
60
Percent
50
40
30
22% gap
52
41
18% gap
17% gap
14% gap
56
58
57
46
48
49
20
10
0
1990
1995
All periods States
SOURCE: National Vital Statistics System, NCHS, CDC
2001
All other States
2002
The Potential Influence of Changes in
the Risk Profile of Births
The Potential Influence of Changes in
the Risk Profile of Births
Increases in <750 gram births were:
- concentrated mostly among 20-34
year old mothers
- occurred for non-Hispanic white, nonHispanic black, and Hispanic mothers
The Potential Influence of Changes in
Medical Management of Pregnancy
Distribution of Births by Gestational
Age: United States, 1990 and 2002
30
25
Percent
20
1990
15
2002
10
5
0
< 24
26
28
30
32
34
36
38
Completed weeks of gestation
SOURCE: National Vital Statistics System, NCHS, CDC
40
42
44
47
Percent of Births with Induction of Labor
by Gestational Age: U.S., 1990-2002
20
18
Moderately preterm (32-36 weeks)
16
Percent
14
12
10
Very preterm (<32 weeks)
8
6
4
2
0
1990
1995
NOTES: Oklahoma did not report induction in 1990.
SOURCE: National Vital Statistics System, NCHS, CDC.
2000
2002
Percent of Births Delivered by Cesarean by
Gestational Age: United States, 1990-2002
60
50
Very preterm (<32 weeks)
Percent
40
30
Moderately preterm (32-36 weeks)
20
10
0
1990
1995
SOURCE: National Vital Statistics System, NCHS, CDC.
2000
2002
Conclusions
2001-2002 infant mortality increase:
• Due almost entirely to an increase in <750
gram births
• ¾ of the increase among singletons
• increase mostly for women aged 20-34
Conclusions (cont.)
• 2003 preliminary infant mortality rate is 6.9
• Not significantly different from 2002 rate
of 7.0
• Preventing very preterm and very low
birthweight deliveries is key to further
lowering the US infant mortality rate.