Infant Mortality: Development of a Proposed Update to the Dollfus Classification of Infant Deaths

County-level Structural Vulnerabilities in Maternal Health and Geographic Variation in Infant Mortality

OBJECTIVE

To evaluate whether community factors that differentially affect the health of pregnant people contribute to geographic differences in infant mortality across the United States.

STUDY DESIGN

This retrospective cohort study sought to characterize the association of a novel composite measure of county-level maternal structural vulnerabilities, the Maternal Vulnerability Index (MVI), with risk of infant death. We evaluated 11,456,232 singleton infants born at 22 0/7 through 44 6/7 weeks' gestation from 2012 to 2014. Using county-level MVI, which ranges from 0-100, multivariable mixed effects logistic regression models quantified associations per 20-point increment in MVI, with odds of death clustered at the county level and adjusted for state, maternal, and infant covariates. Secondary analyses stratified by the social, physical, and health exposures that comprise the overall MVI score. Outcome was also stratified by cause of death.

RESULTS

Odds of death were higher among infants from counties with the greatest maternal vulnerability (0.62% in highest quintile vs 0.32% in lowest quintile, [p<0.001]). Odds of death increased 6% per 20-point increment in MVI (aOR: 1.06, 95% CI 1.04, 1.07). The effect estimate was highest with theme of mental health and substance use (aOR 1.08; 95% CI 1.06, 1.09). Increasing vulnerability was associated with six of seven causes of death.

CONCLUSIONS

Community-level social, physical, and healthcare determinants indicative of maternal vulnerability may explain some of the geographic variation in infant death, regardless of cause of death. Interventions targeted to county-specific maternal vulnerabilities may reduce infant mortality.

Association of State Gestational Age Limit Abortion Laws With Infant Mortality

INTRODUCTION

A growing number of state legislatures have passed laws that restrict access to abortion care after a specified gestational age (gestational age limit laws). The impact of these laws on maternal and child population health outcomes and inequities is unknown. The objective of this study is to determine whether states that implement gestational age limit laws experience subsequent changes in rates of infant mortality.

METHODS

Using U.S. population‒based data from the National Center for Health Statistics Linked Infant Birth-Death Files (2005-2017), difference-in-differences models were estimated using multivariable linear regressions to compare the trends in infant mortality (all-cause and cause-specific rates) in states with gestational age limit laws with the trends in states without such laws. Models stratified by maternal racial/ethnic group explored racial heterogeneity in the law's impact. Data were analyzed in 2020.

RESULTS

This study included 16,232,133 births in states that enacted a gestation age limit abortion law and 36,472,309 births in states that did not from 2005 to 2017. In difference-in-difference analyses, gestational age limit laws were associated with 0.23 excess infant deaths per 1,000 live births (95% CI=0.09, 0.37, p<0.01). In cause-specific analyses, gestational age limit laws were associated with 0.10 additional infant deaths owing to congenital anomalies per 1,000 live births (95% CI=0.03, 0.17, p=0.01). Associations between gestational age limit laws and infant mortality in models stratified by maternal racial/ethnic group were not statistically significant.

CONCLUSIONS

On the basis of data from 2005 to 2017, states that enacted gestational age limit abortion laws subsequently experienced increased infant mortality rates.

The value of autopsy in preterm infants at a Swedish tertiary neonatal intensive care unit 2002-2018

Reliable data on causes of death (COD) in preterm infants are needed to assess perinatal care and current clinical guidelines. In this retrospective observational analysis of all deceased preterm infants born < 37 weeks’ gestational age (n = 278) at a Swedish tertiary neonatal intensive care unit, we compared preliminary COD from Medical Death Certificates with autopsy defined COD (2002–2018), and assessed changes in COD between two periods (period 1:2002–2009 vs. period 2:2011–2018; 2010 excluded due to centralized care and seasonal variation in COD). Autopsy was performed in 73% of all cases and was more than twice as high compared to national infant autopsy rates (33%). Autopsy revised or confirmed a suspected preliminary COD in 34.9% of the cases (23.6% and 11.3%, respectively). Necrotizing enterocolitis (NEC) as COD increased between Period 1 and 2 (5% vs. 26%). The autopsy rate did not change between the two study periods (75% vs. 71%). We conclude that autopsy determined the final COD in a third of cases, while the incidence of NEC as COD increased markedly during the study period. Since there is a high risk to determine COD incorrectly based on clinical findings in preterm infants, autopsy remains a valuable method to obtain reliable COD.

Infant Mortality Associated With Prenatal Opioid Exposure

IMPORTANCE

Knowledge of health outcomes among opioid-exposed infants is limited, particularly for those not diagnosed with neonatal opioid withdrawal syndrome (NOWS).

OBJECTIVES

To describe infant mortality among opioid-exposed infants and identify how mortality risk differs in opioid-exposed infants with and without a diagnosis of NOWS compared with infants without opioid exposure.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study of maternal-infant dyads was conducted, linking health care claims with vital records for births from January 1, 2010, to December 31, 2014, with follow-up of infants until age 1 year (through 2015). Maternal-infant dyads were included if the infant was born in Texas at 22 to 43 weeks' gestational age to a woman aged 15 to 44 years insured by Texas Medicaid. Data analysis was performed from May 2019 to October 2020.

EXPOSURE

The primary exposure was prenatal opioid exposure, with infants stratified by the presence or absence of a diagnosis of NOWS during the birth hospitalization.

MAIN OUTCOMES AND MEASURES

Risk of infant mortality (death at age <365 days) was examined using Kaplan-Meier and log-rank tests. A series of logistic regression models was estimated to determine associations between prenatal opioid exposure and mortality, adjusting for maternal and neonatal characteristics and clustering infants at the maternal level to account for statistical dependence owing to multiple births during the study period.

RESULTS

Among 1 129 032 maternal-infant dyads, 7207 had prenatal opioid exposure, including 4238 diagnosed with NOWS (mean [SD] birth weight, 2851 [624] g) and 2969 not diagnosed with NOWS (mean [SD] birth weight, 2971 [639] g). Infant mortality was 20 per 1000 live births for opioid-exposed infants not diagnosed with NOWS, 11 per 1000 live births for infants with NOWS, and 6 per 1000 live births in the reference group (P < .001). After adjusting for maternal and neonatal characteristics, mortality in infants with a NOWS diagnosis was not significantly different from the reference population (odds ratio, 0.82; 95% CI, 0.58-1.14). In contrast, the odds of mortality in opioid-exposed infants not diagnosed with NOWS was 72% greater than the reference population (odds ratio, 1.72; 95% CI, 1.25-2.37).

CONCLUSIONS AND RELEVANCE

In this study, opioid-exposed infants appeared to be at increased risk of mortality, and the treatments and supports provided to those diagnosed with NOWS may be protective. Interventions to support opioid-exposed maternal-infant dyads are warranted, regardless of the perceived severity of neonatal opioid withdrawal.

The Unrecognized Mortality Burden of Genetic Disorders in Infancy

Objectives. To determine how deaths of infants with genetic diagnoses are described in national mortality statistics. Methods. We present a retrospective cohort study of mortality data, obtained from the National Death Index (NDI), and clinical data for 517 infants born from 2011 to 2017 who died before 1 year of age in the United States. Results. Although 115 of 517 deceased infants (22%) had a confirmed diagnosis of a genetic disorder, only 61 of 115 deaths (53%) were attributed to International Classification of Diseases, 10th Revision codes representing congenital anomalies or genetic disorders (Q00-Q99) as the underlying cause of death because of inconsistencies in death reporting. Infants with genetic diagnoses whose underlying causes of death were coded as Q00-Q99 were more likely to have chromosomal disorders than monogenic conditions (43/61 [70%] vs 18/61 [30%]; P < .001), which reflects the need for improved accounting for monogenic disorders in mortality statistics. Conclusions. Genetic disorders, although a leading cause of infant mortality, are not accurately captured by vital statistics. Public Health Implications. Expanded access to genetic testing and further clarity in death reporting are needed to describe properly the contribution of genetic disorders to infant mortality.

Privilege and deprivation in Detroit: infant mortality and the Index of Concentration at the Extremes

BACKGROUND

Enhanced understanding of spatial social polarization as a determinant of infant mortality is critical to efforts aimed at advancing health equity. Our objective was to identify associations between spatial social polarization and risk of infant death.

METHODS

We conducted a cross-sectional analysis of all birth records issued to non-Hispanic (NH) Black and White women in Wayne County, MI, from 2010 to 2013 (n = 84 159), including linked death records for deaths occurring at less than 1 year of age. Spatial social polarization was measured in each Census tract of maternal residence (n = 599) using the Index of Concentration at the Extremes (ICE)-a joint measure of racial and economic segregation-estimated from American Community Survey 2009-2013 data. Log-Poisson regression models quantified relative risk (RR) of infant death (all-cause and cause-specific) associated with tertiles of the index, adjusting for maternal demographic characteristics and tract-level poverty.

RESULTS

The crude infant-mortality rate was more than 2-fold higher among NH Black infants compared with NH Whites (14.0 vs 5.9 deaths per 1000 live births). Half of the 845 infant deaths (72% NH Black, 28% NH White) occurred in tracts in the lowest tertile of the ICE distribution, representing areas of relative deprivation. After adjustments, risk of death among infants in the lowest tertile was 1.46 times greater than those in the highest tertile (adjusted infant-mortality rate = 3.7 deaths per 1000 live births in highest tertile vs 5.4 deaths per 1000 live births in lowest tertile, relative risk = 1.46, 95% confidence interval = 1.02, 2.09). Patterns of associations with the index differed by cause of death.

CONCLUSIONS

These findings suggest efforts to support equitable community investments may reduce incidents of death and the disproportionate experience of loss among NH Black women.

Estimating the Burden of Prematurity on Infant Mortality: A Comparison of Death Certificates and Child Fatality Review in Ohio, 2009-2013

Introduction Infant mortality is a key population health indicator, and accurate cause of death reporting is necessary to design infant mortality prevention strategies. Death certificates and child fatality review (CFR) both track leading infant causes of death in Ohio but produce different results. Our aim was to determine the frequency and characteristics of differences between the two systems to understand both cause of death ranking systems for Ohio. Methods We linked and analyzed data from death certificates and CFR records for all infant deaths (aged < 1 year) in Ohio during 2009-2013. Death certificate and CFR cause of death assignments were compared. Kappa statistic was used to measure concordance. Death certificate-CFR cause of death pairs were plotted to identify common concordant and discordant pairs. Results A total of 5030 infant deaths with death certificate and CFR records were analyzed. The most common discordant cause of death pair was other perinatal condition on the death certificate and prematurity by CFR (1119). Specific injury categories had higher concordance (kappa 0.71-1.00) than medical categories (kappa 0.00-0.78). Among 456 deaths categorized as sudden infant death syndrome on death certificates, approximately 50% (230) were categorized as missing, unknown, or undetermined by CFR. Discussion Linking death certificate and CFR causes of death provided a more robust understanding of infant causes of death in Ohio. Separately, each system serves distinct and valuable purposes that should be reviewed before selecting one system for ranking leading causes of infant mortality.