Danielle Sollers

1
Workshop 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
2
State 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

3
Toolkit Framework
State Infant Mortality Toolkit
Stage 1 Overview Investigation
Stage 2 Focused Investigation
4
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
5
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
6
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
7
U
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
8
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
9
Stage 1 Hypotheses Assessment of Changes in
Maturity at Birth and Maturity-Specific Mortality
State Infant Mortality Toolkit

• The Maturity and Maturity-Specific Mortality
  Subgroup

10
Data

• 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.

11
Data 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.

12
Maturity 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.

13
Maturity 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.

14
Maturity 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.

15
Birth Weight Distribution Changes1985-88 to
1995-2000
16
Birth 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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Birth 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
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Birth 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
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Changes 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
22
Birth 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.

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Changes in Patternsof Fetal Growth1985-88 to
1995-2000
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Birth 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
26
Birth 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
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Birth 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
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Fetal 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.

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Temporal 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
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Recent Trends in Birth Outcome Measures
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Maturity Mortality TrendsUSA
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Maturity Mortality TrendsHawaii
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Overall 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.

34
Suggested 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.

35
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
36
Maturity 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

37
Maturity 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.

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Maturity 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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Recent Trends in Birth Outcome Measures
42
Maturity Mortality TrendsUSA
43
Maturity Mortality TrendsHawaii
44
Summary

• 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.

45
Suggested 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.

46
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
47
Stage 1 State Assessment of
Timing Cause of Death
State Infant Mortality Toolkit

• Thought Different biologic causes may be
  impacting mortality

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Study 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?

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Possible 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.

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Timing 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.

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Classification 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

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Methods for classifying cause of death

• Wigglesworth
• Aberdeen
• Necropsy findings
• Naeyes Classification
• NICE
• Dollfus
• ICE
• NCHS

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Why 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

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Modified 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
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What 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.

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Steps 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

57
Study and comparison populations

• Study population
• North Carolina
• 1991-1993 compared to 2001-2003
• Comparison population
• U.S.
• 1991 compared to 2001-2002

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North 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.

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North 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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Data 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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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

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Cause-specific infant mortality rates in North
Carolina, 2001-2003 and the U.S., 2001-2002
65
Issues 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

66
Toolkit Framework
Stage 1 Overview Investigation
Maturation-Specific
Maturation
Data Reporting
Age Cause
Stage 2 Focused Investigation
Environmental Attributes
Maternal Attributes
Health Services
67
Stage 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.

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Reported Vital Events
Conception
1 Year
Live Birth
Gestation
Infancy
20 wks
4 wks
Infant Death
Fetal Death
Feto-Infant Death
69
Fetal 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?

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Fetal 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

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Five-year Fetal Mortality Rates by Birthweight
Delaware, 1989-2002
72
Number of States by Percent of All Fetal Deaths
20 to 27 Weeks Gestation, 2000-02
73
So 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

74
Live Births In-State Trends

• Reporting
• Change in reporting regulation, process, or
  training?
• Clarification of viability or gestation?
• Change in quality processing?

75
Live 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

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Percent of All Live Births by BirthweightLouisian
a, 1995-2002
77
Number of States by Percent of All Live Birth
lt1,500 Grams, 2000-02
78
Percentage of All Live Births lt1,500 Grams,
2000-02
79
So 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

80
Infant 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?

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Infant 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

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Infant 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

83
Infant Mortality Rates for lt500g Live
BirthsLouisiana US
84
Number of States by Infant Mortality Rates,
2000-02
85
Infant Mortality Rates, 2000-02
86
So 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

87
Potential Reporting Problems by
Birthweight Below
1.0 Standard Deviation
Fetal Deaths Fetal/Infant Deaths
Infant Deaths Infant Deaths/Births
Live Births All Three
88
Suggested 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.