Title: Danielle Sollers
1Workshop Investigating High or Increased Infant
Mortality Rates
State Infant Mortality Toolkit
Session Leaders
- Danielle SollersAMCHP
- William SappenfieldCDC
- Greg AlexanderUSF
11th Annual MCH EPI Conference
Miami, FL Dec. 10, 2005
2State Infant Mortality Toolkit Workshop
- Background on SIMC
- SIMC Toolkit Overview, Framework, and Next Steps
- Stage 1 Framework Components
- Maturation
- Maturation-specific mortality
- Age and Cause of Death
- Vital Records Reporting
3Toolkit Framework
State Infant Mortality Toolkit
Stage 1 Overview Investigation
Stage 2 Focused Investigation
4Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
5Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
6Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
7U
A
B
SCHOOL OF PUBLIC HEALTH
Maternal and Child Health
Infant Mortality Assessment
Manual Greg R. Alexander, RS, MPH, ScDSara
Nabukera, M.D., MPHDeren Bader, MPHMartha
Slay-Wingate, MPH University of Alabama at
BirminghamSchool of Public HealthDepartment of
Maternal and Child Health
Introduction Purposes and Objectives Data
Sources Questions for Assessment Statistical
Analysis and Interpretation SAS
Program References Appendix Home
Website http//www.soph.uab.edu/mch-imrm/index.ht
m
8Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
9Stage 1 Hypotheses Assessment of Changes in
Maturity at Birth and Maturity-Specific Mortality
State Infant Mortality Toolkit
- The Maturity and Maturity-Specific Mortality
Subgroup
10Data
- In order to explore proposed birth
maturity-related hypotheses that might explain
infant mortality trends and develop examples for
the SIMC Toolkit, we selected the following NCHS
datasets - U.S. Live Birth Cohort Linked files for 1985-1988
and 1995-2000 - U.S. Fetal Death files 1985-1989 and 1995-2000.
11Data Selection
- For this presentation we used the following case
selection criteria - Live births (1985-1988 and 1995-2000) to U.S.
resident mothers - Fetal deaths were excluded.
12Maturity Hypothesis for Trends in Infant Mortality
- Formal Hypothesis
- There is no association between the currently
observed trends in infant mortality and any
changes in the maturity at birth of infants as
measured by birth weight, gestational age and
fetal growth, e.g., small for gestational age.
13Maturity Hypothesis for Trends in Infant Mortality
- Rationale
- One of the strongest predictors of infant death
is the maturity of an infant at birth with
infants at the extremes of maturity being at
highest risk. - As infant mortality trends may be driven by
changes in the proportion of these high risk
infants, the examination trends in birth weight
gestational age distributions is indicated.
14Maturity Hypothesis for Trends in Infant Mortality
- Possible Pathways
- Changes in proportion of high risk birth weight
or gestational age infants, e.g., increase in
very preterm or very low birth weight rates - Changes in proportion of small-for-gestational
age infants.
15Birth Weight Distribution Changes1985-88 to
1995-2000
16Birth Weight Distribution1985-88 1995-2000
Birth Weight Distribution 1985-88 1985-88 1995-2000
Mean 3348 3348 3320
Median 3374 3374 3360
Temporal change in mean BW based on parameter estimate from regression analysis Temporal change in mean BW based on parameter estimate from regression analysis Temporal change in mean BW based on parameter estimate from regression analysis Temporal change in mean BW based on parameter estimate from regression analysis
Unadjusted Unadjusted -27.56 (SE 0.20) -27.56 (SE 0.20)
Adjusted (maternal age, race, marital status, education, parity, number at birth and prenatal care utilization) (also adjusting for gest. age) Adjusted (maternal age, race, marital status, education, parity, number at birth and prenatal care utilization) (also adjusting for gest. age) -1.01 (SE 0.21) 21.47 (SE 0.18) -1.01 (SE 0.21) 21.47 (SE 0.18)
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19Birth Weight Categories1985-88 1995-2000
Birth weight categories 1985-88 1995-2000
lt500g 0.13 0.15
VLBW (lt1500g) 1.23 1.43
MLBW (1500-2499g) 5.62 6.09
LBW (lt2500g 6.85 7.52
NBW (2500-3999g) 82.10 82.39
HBW (4000g) 11.06 10.09
20Birth Weight Categories1985-88 1995-2000
High Birth Weight Categories 1985-88 1995-2000
HBW (4000g) 11.06 10.09
Macrosomic I (4000-4499g) 9.17 8.54
Macrosomic II (4500-4499g) 1.67 1.39
Macrosomic III (5000g) 0.22 0.16
21Changes in Birth Weight Categories by State
1985-1888 1995-2000
State VLBW VLBW LBW LBW
State 1985-1988 1995-2000 1985-1988 1995-2000
Delaware 1.54 1.83 7.20 8.57
Hawaii 1.05 1.17 6.81 7.39
Louisiana 1.62 2.04 8.70 10.06
Missouri 1.21 1.40 6.84 7.68
North Carolina 1.55 1.88 7.93 8.81
22Birth Weight DistributionComments
- Slight decrement in BW distribution between
1985-88 and 1995-2000 with increases in lt500g,
VLBW, and LBW rates, although macrosomic (4000g)
birth rates have decreased. - Similar trends evident in each target State.
- Evidence suggests there has been an increase in
rate of births with birth weights at the lower
extreme of the BW distribution.
23Changes in Patternsof Fetal Growth1985-88 to
1995-2000
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25Birth Weight for Gestational Age Categories
Fetal growth categories 1985-88 1995-00
SGA 10.57 10.10
AGA 78.25 79.16
LGA 11.17 10.75
based on 1991 US reference curve for singleton live births based on 1991 US reference curve for singleton live births based on 1991 US reference curve for singleton live births
26Birth Weight for Gestational Age Categories
Fetal growth categories 1985-88 1995-00
Preterm, lt2500g 3.95 4.95
Preterm, 2500g 5.70 6.21
Term, lt2500g 2.70 2.56
Term SGA 9.42 8.59
Preterm SGA 1.16 1.51
27Birth Weight for Gestational Age Category (SGA)
by State 1985-88, 1998-2000
State SGA SGA
State 1985-88 1995-2000
Delaware 10.87 9.63
Hawaii 12.62 11.45
Louisiana 13.14 12.81
Missouri 10.66 9.94
North Carolina 11.43 10.90
28Fetal Growth PatternsComments
- Change in gestational age reporting between time
periods made have altered shape of fetal growth
patterns (note decline in both SGA and LGA). - SGA rates have declined, driven by decrease for
term SGA infants. - Preterm SGA rates have increased.
29Temporal Change in Outcomes1985-88 (reference)
1995-2000
Outcome Parameters Unadjusted OR (95CI) Adjusted OR (95 CI)
VLBW 1.167 (1.160-1.173) 0.976 (0.970-0.983)
LBW 1.106 (1.103-1.108) 0.945 (0.942-0.948)
SGA 0.950 (0.948-0.952) 0.908 (0.906-0.910)
Preterm 1.176 (1.173-1.178) 1.010 (1.007-1.013)
IMR 0.707 (0.702-0.712) 0.638 (0.633-0.643)
Adjusted for maternal age, race, marital status, education, parity, number at birth and prenatal care utilization Adjusted for maternal age, race, marital status, education, parity, number at birth and prenatal care utilization Adjusted for maternal age, race, marital status, education, parity, number at birth and prenatal care utilization
30Recent Trends in Birth Outcome Measures
31Maturity Mortality TrendsUSA
32Maturity Mortality TrendsHawaii
33Overall Changes in Maturity at DeliveryPreliminar
y Summary
- During the last period, preterm, VLBW and LBW
rates rose while infant mortality rate continued
to decline. - While there is some evidence of a decrement in
maturity at birth that could negatively influence
infant mortality rates, improvement in infant
mortality for the U.S. generally continued,
suggesting that factors other than maturity at
birth had a greater impact on infant mortality
trends.
34Suggested References
- Alexander GR, Allen MC. Conceptualization,
measurement, and use of gestational age. I.
Clinical and public health practice. J Perinatol
1996 16(1) 53-59. - Alexander GR, Slay M. Prematurity at birth
Trends, racial disparities, and epidemiology.
Mental Retard Develop Disabilities Res Reviews
2002 8 215-220 - Blondel B, Kogan, MD, et al. The impact of the
increasing number of multiple births on the rates
of preterm birth and low birth weight An
international study. Am J Public Health 2002
921323-1330. - Demissie K, Rhoads GG, et al. Trends in preterm
birth and neonatal mortality among blacks and
whites in the United States from 1989 to 1996.
Am J Epid 2001 154307-315. - Kramer MS. Intrauterine growth and gestational
duration determinants. Pediatrics 1987 80
502-11. - McCormick MC. Significance of low birth weight
for infant mortality and morbidity. Birth Defects
Orig Artic Ser 1988243-10. - Oken E, Kleinman KP, et al. A nearly continuous
measure of birth weight for gestational age using
a United States national reference. BMC Pediatr
2003 36. - Wilcox LS, Marks JS, eds. From Data to Action.
Atlanta Centers for Disease Control, 1994, pp
163-178.
35Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
36Maturity Specific Mortality Hypothesis for Trends
in Infant Mortality
- Formal Hypothesis
- There is no association between the currently
observed trends in infant mortality and any
changes in mortality risk for specific maturity
at birth categories, as measured by birth weight,
gestational age and fetal growth, e.g., small for
gestational age
37Maturity Hypothesis for Trends in Infant Mortality
- Rationale
- Overall infant mortality trends may be driven by
changes in the risk of mortality for specific
maturity at birth groups, e.g., increases in the
survival of VLBW infants may have a marked effect
on overall infant mortality rates. - Therefore, trends in birth weight/gestational age
specific infant mortality rates should be
examined.
38Maturity Specific Mortality Hypothesis for Trends
in Infant Mortality
- Possible Pathways
- Changes in birth weight or gestational
age-specific survival, e.g., no temporal
improvement in survival for lt1000 gram or lt24
week infants - Changes in survival of small-for-gestational age
infants.
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41Recent Trends in Birth Outcome Measures
42Maturity Mortality TrendsUSA
43Maturity Mortality TrendsHawaii
44Summary
- Both birth weight and gestational age specific
mortality have improved nationwide, although such
recent trends are not evident in every State,
e.g., Hawaii. - These data suggest that the investigation of
maturity-specific mortality is a viable
hypothesis to explore for better understanding
trends in infant mortality.
45Suggested References
- Alexander, GR, Kogan M, et al. U.S. birth
weight-gestational age-specific neonatal
mortality 1995-7 rates for Whites, Hispanics and
African-Americans. Pediatrics 2003 111(1)
e61-66. - Alexander GR, Tompkins ME, at el. Trends and
racial differences in birth weight and related
survival. MCHJ 1999 3(1) 71-79. - Allen MC, Alexander GR, et al. Racial differences
in temporal changes in newborn viability and
survival by gestational age. Paediatr Perinat
Epid 2000 14(2) 152-158. - Kleinman JC, Kovar MG, et al. A comparison of
1960 and 1973-4 early neonatal mortality in
selected states. Am J Epid 1978 108 454-469. - Lee KS, Paneth N, et al. Neonatal mortality an
analysis of the recent improvement in the United
States. Am J Public Health 1980 7015-21. - Lee KS, Paneth N, et al. The very
low-birth-weight rate Principal predictor of
neonatal mortality in industrialized populations.
J Pediatr 1980 97759-64. - Lee KS, Khoshnood B, et al. Which birth weight
groups contributed most to the overall reduction
in the neonatal mortality rate in the United
States from 1960 to 1986? Paediatr Perinat Epid
1995 9420-30. - Sappenfield WM, Buehler JW, et al. Differences in
neonatal and postneonatal mortality by race,
birth weight, and gestational age. Public Health
Rep. 1987 102(2) 182-192.
46Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
47Stage 1 State Assessment of
Timing Cause of Death
State Infant Mortality Toolkit
- Thought Different biologic causes may be
impacting mortality
48Study question
- To what degree could changes in the cause and
timing of death explain - Currently observed trends in fetal infant
mortality rate? - Disparities in infant mortality?
- Differences between states?
49Possible pathways to be explored
- Changes in
- specific cause(s) of death
- after accounting for possible changes in
classification and certification preference - timing of death (age at death)
- cause and/or timing of death within specific
categories of birthweight, gestational age,
race/ethnicity, etc.
50Timing definitions for infant mortality
- Early fetal death A fetal death between 20 and
27 weeks of gestation. - Late fetal death A fetal death after 28 weeks of
gestation or more. - Neonatal death A death of a liveborn under 28
days of age. - Early neonatal death A death of a liveborn under
7 days of age. - Late neonatal death A death of a live born
occurring between 7 and 27 days of age. - Postneonatal death A death occurring between 28
days and 11 months of age. - Infant death A death of a live born under 1 year
of age.
51Classification system for cause of death is
needed because
- The number of individual ICD codes is
unmanageable - Individual codes are sensitive to changes in
classification preference - Individual codes are less comparable over time
(ICD-9 to ICD-10) - Classification allows one to organize data for
analytic and programmatic purposes
52Methods for classifying cause of death
- Wigglesworth
- Aberdeen
- Necropsy findings
- Naeyes Classification
- NICE
- Dollfus
- ICE
- NCHS
53Why recommend themodified Dollfus method
- Has only 9 categories
- Good ICD-9 to ICD-10 comparability ratios
- Practical and preventive perspective
- Developed by a North Carolina researcher
54Modified Dollfus classifications (and associated
ICD9-to-ICD10 comparability ratios courtesy of
Donna Hoyert, NCHS)
Cause of Infant Death Comparability Ratio
1. Prematurity and related conditions 1.031
2. Congenital anomaly 0.928
3. SIDS and SUID 1.017
4. Obstetric conditions 1.021
5. Birth asphyxia 1.325
6. Perinatal Infections 1.026
7. Other infections 0.746
8. External causes/Injuries 0.998
9. All other 1.072
Does not apply to fetal deaths
55What to do with small numbers in stratified
analyses?
- The NCHS doesnt show the value of a rate when
the cell has fewer than 20 cases. - Value based on 20 deaths would exceed a relative
standard error of 23. - General rule rates with a numerator lt20 are
unstable - Consider reporting 95 confidence intervals
- If stratification leads to small numbers, either
omit a stratification variable or combine levels.
56Steps in assessing changes in infant mortality
- Plan the analysis
- Outcomes (rates and percent change)
- Timing of death
- Cause of death
- Morbidity/VLBW
- Stratification factors to consider
- Age of mother
- Plurality
- Gestational age
- Race/ethnicity
- Birthweight
- Significance Testing
57Study and comparison populations
- Study population
- North Carolina
- 1991-1993 compared to 2001-2003
- Comparison population
- U.S.
- 1991 compared to 2001-2002
58North Carolina data required
- Best datasets for this analysis
- Linked birth-infant death files (birth cohort)
- Fetal death files
- Live birth files
- In North Carolina and U.S.
59North Carolina Analysis
- Calculate cause-specific infant mortality rates
and proportionate mortality - Calculate percent change in rates over time
periods - Determine if the change is significant
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61Data analysis North CarolinaTiming of death
infant and fetal periods
1991-1993 2001-2003 Percent Change
Infant mortality rate 10.2 8.2 -19.6
Fetal mortality rate 8.8 7.2 -18.2
Fetal-infant mortality rate 18.9 15.4 -18.5
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63 More data analyses national comparisons
- Advantages
- Determine specific infant mortality rates and
compare to the US national infant mortality rates - Provides context for analyses
- Disadvantages
- Availability of comparable data
- Years
- Race/ethnicity categories
64Cause-specific infant mortality rates in North
Carolina, 2001-2003 and the U.S., 2001-2002
65Issues and limitations
- Other sources of data
- Files linked to hospital discharge may be helpful
with co-morbidities - Homogeneity assumption
- States have different racial/ethnic and other
subpopulations - Causes of death may not be reported the same
Years to choose
66Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
67Stage 1 State Assessment of
Vital Records Reporting
State Infant Mortality Toolkit
- Thought State infant mortality rates and trends
may not be real and may be artificially
impacted by vital records reporting.
68Reported Vital Events
Conception
1 Year
Live Birth
Gestation
Infancy
20 wks
4 wks
Infant Death
Fetal Death
Feto-Infant Death
69Fetal Deaths In-State Trends
- Reporting
- Change in reporting regulation, process, or
training? - Clarification of viability or gestation?
- Change in quality processing?
- Change in abortion reporting?
70Fetal Deaths In-State Trends
- Data Analysis
- Number and percentage of unknown birthweight and
gestational age - Percentages and mortality rates by birthweight
and gestational age - Percentage of all deaths 20-27 weeks gestational
age
71Five-year Fetal Mortality Rates by Birthweight
Delaware, 1989-2002
72Number of States by Percent of All Fetal Deaths
20 to 27 Weeks Gestation, 2000-02
73So What?
- Assumptions
- The real percentage of 20-27 wks is 73
- Your states percentage is 35 or 35 deaths of
100 deaths - (35 ?) / (100 ?) 73
- Answer 143 additional deaths
74Live Births In-State Trends
- Reporting
- Change in reporting regulation, process, or
training? - Clarification of viability or gestation?
- Change in quality processing?
75Live Births In-State Trends
- Data Analysis
- Percentages by birthweight and gestational age
especially lt500 grams and lt24 weeks gestational
age - Changes in distribution
- Focus on very premature and very low birthweight
births - Overall and race categories
76Percent of All Live Births by BirthweightLouisian
a, 1995-2002
77Number of States by Percent of All Live Birth
lt1,500 Grams, 2000-02
78Percentage of All Live Births lt1,500 Grams,
2000-02
79So What?
- Assumptions
- The real percentage of lt500 g live births is
0.30 - Your states percentage is 0.20
- The real mortality rate is 900/1000
- (.30-.20) .900 .09
- Answer 1 per 1,000 IMR increase
80Infant Deaths In-State Trends
- Reporting
- Change in reporting regulation, process, or
training? - Change in the linkage of infant deaths to live
births? - Change in quality processing?
- Change in follow up of lt750 gram live births with
delivery hospitals?
81Infant Deaths In-State Trends
- Data Analysis
- Number and percentage of unlinked death records
- Number and percentage of unknown birthweight and
gestational age - Percentages and mortality rates by birthweight
and gestational age - Percentage and mortality rates by state of death
82Infant Deaths In-State Trends
- Data Analysis
- Mortality rates of infants who die soon after
birth - Feto-infant deaths and mortality rates
- Compare fetal, infant, and feto-infant mortality
rates
83Infant Mortality Rates for lt500g Live
BirthsLouisiana US
84Number of States by Infant Mortality Rates,
2000-02
85Infant Mortality Rates, 2000-02
86So What?
- Assumptions
- The real IMR of lt500 g is 900/1000
- Your states IMR is 700/1000
- The states percentage of lt500 g live births is
0.30 - (.900-.700) .30 .06
- Answer 0.6 per 1000 IMR increase
87Potential Reporting Problems by
Birthweight Below
1.0 Standard Deviation
Fetal Deaths Fetal/Infant Deaths
Infant Deaths Infant Deaths/Births
Live Births All Three
88Suggested References
- Fetal Death Reporting
Martin and Hoyert - Reporting lt500 Gram Live Births Wilson,
Fenton, Munson - Importance of Looking at Very Low
Birthweight-Specific Mortality MacDorman,
Martin, Mathews, et al. - Gestational Age Reporting Alexander,
Tompkins, Cornely - Reliability of Birth Certificate Data
DiGiuseppe, Aron, Ranbom, et al.