Factors that mediate racial/ethnic disparities in US fetal death rates

The association of maternal country/region of origin and nativity with infant mortality rate among Hispanic preterm infants

OBJECTIVES

Among US-born preterm infants of Hispanic mothers, we analyzed the unadjusted and adjusted infant mortality rate (IMR) by country/region of origin and maternal nativity status.

STUDY DESIGN

Using linked national US birth and death certificate data (2005-2014), we examined preterm infants of Hispanic mothers by subgroup and nativity. Clinical and sociodemographic covariates were included and the main outcome was death in the first year of life.

RESULTS

In our cohort of 891,216 preterm Hispanic infants, we demonstrated different rates of infant mortality by country and region of origin, but no difference between infants of Hispanic mothers who were US vs. foreign-born.

CONCLUSION

These findings highlight the need to disaggregate the heterogenous Hispanic birthing population into regional and national origin groups to better understand unique factors associated with adverse perinatal outcomes in order to develop more targeted interventions for these subgroups.

Stillbirth After Adolescent and Young Adult Cancer: A Population-Based Study

BACKGROUND

Gonadotoxic effects of cancer treatment may increase risk of adverse birth outcomes in adolescent and young adult (AYA, aged 15-39 years) women diagnosed with cancer. We estimated risk of stillbirth (fetal death of gestational age ≥20 weeks or weighing ≥350 grams) in a population-based sample of AYA women.

METHODS

AYA women diagnosed with cancer between January 1, 1995, and December 31, 2015, were identified using the Texas Cancer Registry and linked to live birth and fetal death certificates through December 31, 2016. Among AYA women, cumulative incidence of stillbirth was estimated by gestational age, and Poisson regression models identified factors associated with stillbirth. Standardized fetal mortality ratios (SMR) compared the observed fetal mortality rate in AYA women with the expected fetal mortality rate in the general population.

RESULTS

A total of 11 628 live births and 68 stillbirths occurred to 8402 AYA women after diagnosis. Cumulative incidence of stillbirth in AYA women was 0.70% (95% confidence interval [CI] = 0.51% to 0.96%) at 40 weeks of gestation. Risk of stillbirth was higher among Hispanic (risk ratio [RR] = 2.64, 95% CI = 1.29 to 5.41) and non-Hispanic Black (RR = 4.13, 95% CI = 1.68 to 10.16) women compared with non-Hispanic White women; there was no association with receipt of chemotherapy or time since diagnosis. Age- and race and ethnicity-adjusted fetal mortality rate in AYA women was similar to the general population (SMR = 0.99, 95% CI = 0.77 to 1.26).

CONCLUSIONS

AYA women may be counseled that overall risk of stillbirth is low, and for most, cancer does not appear to confer additional risk.

Racial and ethnic disparities in outcomes after NICU discharge: An equity-focused model

Significant racial and ethnic disparities exist in birth outcomes and complications related to prematurity. However, little is known about racial and ethnic variations in health outcomes after premature infants are discharged from the neonatal intensive care unit (NICU). We propose a novel, equity-focused conceptual model to guide future evaluations of post-discharge outcomes that centers on a multi-dimensional, comprehensive view of health, which we call thriving. We then apply this model to existing literature on post-discharge inequities, revealing a need for rigorous analysis of drivers and strength-based, longitudinal outcomes.

The Unequal Impact of the COVID-19 Pandemic on Infant Health

The COVID-19 pandemic has taken a large toll on population health and well-being. We examine the consequences of prenatal exposure for infant health, through which the pandemic may have lasting intergenerational effects. We examine multiple pathways by which the pandemic shaped birth outcomes and socioeconomic disparities in these consequences. Analysis of more than 3.5 million birth records in California with universal information on COVID infection among persons giving birth at the time of delivery reveals deep inequalities in infection by education, race/ethnicity, and place-based socioeconomic disadvantage. COVID infection during pregnancy, in turn, predicts a large increase in the probability of preterm birth, by approximately one third. At the population level, a surprising reduction in preterm births during the first months of the pandemic was followed by an increase in preterm births during the surge in COVID infections in the winter of 2021. Whereas the early-pandemic reduction in preterm births benefited primarily highly educated mothers, the increase in preterm births during the winter infection surge was entirely concentrated among mothers with low levels of schooling. The COVID-19 pandemic is expected to exacerbate U.S. inequality in multiple ways. Our findings highlight a particularly enduring pathway: the long-term legacy of prenatal exposure to an unequal pandemic environment.

Ethnic disparities in stillbirth risk in Yunnan, China: a prospective cohort study, 2010-2018

Background

Racial and ethnic disparities in stillbirth risk had been documented in most western countries, but it remains unknown in China. This study was to determine whether exist ethnic disparities in stillbirth risk in mainland China.

Methods

Pregnancy outcomes and ethnicity data were obtained from the National Free Preconception Health Examination Project (NEPHEP), a nationwide prospective population-based cohort study conducted in Yunnan China from 2010-2018. The Han majority and other four main minorities including Yi, Dai, Miao, Hani were investigated in the analysis. The stillbirth hazards were estimated by life-table analysis. The excess stillbirth risk (ESR) was computed for Chinese minorities using multivariable logistic regression.

Results

Compared with other four minorities, women in Han majority were more likely to more educated, less multiparous, and less occupied in agriculture. The pattern of stillbirth hazard of Dai women across different gestation intervals were found to be different from other ethnic groups, especially in 20-23 weeks with 3.2 times higher than Han women. The ESR of the Dai, Hani, Miao, and Yi were 45.05, 18.70, -4.17 and 12.28%, respectively. Adjusted for maternal age, education, birth order and other general risk factors, the ethnic disparity still persisted between Dai women and Han women. Adjusted for preterm birth further (gestation age <37 weeks) can reduce 16.91% ESR of Dai women and made the disparity insignificant. Maternal diseases and congenital anomalies explained little for ethnic disparities.

Conclusions

We identified the ethnic disparity in stillbirth risk between Dai women and Han women. General risk factors including sociodemographic factors and maternal diseases explained little. Considerable ethnic disparities can be attributed to preterm birth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-10102-y.

Socioeconomic Mediators of Racial and Ethnic Disparities in Congenital Heart Disease Outcomes: A Population-Based Study in California

Background

Racial/ethnic and socioeconomic disparities exist in outcomes for children with congenital heart disease. We sought to determine the influence of race/ethnicity and mediating socioeconomic factors on 1‐year outcomes for live‐born infants with hypoplastic left heart syndrome and dextro‐Transposition of the great arteries.

Methods and Results

The authors performed a population‐based cohort study using the California Office of Statewide Health Planning and Development database. Live‐born infants without chromosomal anomalies were included. The outcome was a composite measure of mortality or unexpected hospital readmissions within the first year of life defined as >3 (hypoplastic left heart syndrome) or >1 readmissions (dextro‐Transposition of the great arteries). Hispanic ethnicity was compared with non‐Hispanic white ethnicity. Mediation analyses determined the percent contribution to outcome for each mediator on the pathway between race/ethnicity and outcome. A total of 1796 patients comprised the cohort (n=964 [hypoplastic left heart syndrome], n=832 [dextro‐Transposition of the great arteries]) and 1315 were included in the analysis (n=477 non‐Hispanic white, n=838 Hispanic). Hispanic ethnicity was associated with a poor outcome (crude odds ratio, 1.72; 95% confidence interval [CI], 1.37–2.17). Higher maternal education (crude odds ratio 0.5; 95% CI, 0.38–0.65) and private insurance (crude odds ratio, 0.65; 95% CI, 0.45–0.71) were protective. In the mediation analysis, maternal education and insurance status explained 33.2% (95% CI, 7–66.4) and 27.6% (95% CI, 6.5–63.1) of the relationship between race/ethnicity and poor outcome, while infant characteristics played a minimal role.

Conclusions

Socioeconomic factors explain a significant portion of the association between Hispanic ethnicity and poor outcome in neonates with critical congenital heart disease. These findings identify vulnerable populations that would benefit from resources to lessen health disparities.

Racial and Ethnic Disparities in Preterm Infant Mortality and Severe Morbidity: A Population-Based Study

BACKGROUND

Disparities exist in the rates of preterm birth and infant mortality across different racial/ethnic groups. However, only a few studies have examined the impact of race/ethnicity on the outcomes of premature infants.

OBJECTIVE

To report the rates of mortality and severe neonatal morbidity among multiple gestational age (GA) groups stratified by race/ethnicity.

METHODS

A retrospective cohort study utilizing linked birth certificate, hospital discharge, readmission, and death records up to 1 year of life. Live-born infants ≤36 weeks born in the period 2007-2012 were included. Maternal self-identified race/ethnicity, as recorded on the birth certificate, was used. ICD-9 diagnostic and procedure codes captured neonatal morbidities (intraventricular hemorrhage, retinopathy of prematurity, periventricular leukomalacia, bronchopulmonary dysplasia, and necrotizing enterocolitis). Multiple logistic regression was performed to evaluate the impact of race/ethnicity on mortality and morbidity, adjusting for GA, birth weight, sex, and multiple gestation.

RESULTS

Our cohort totaled 245,242 preterm infants; 26% were white, 46% Hispanic, 8% black, and 12% Asian. At 22-25 weeks, black infants were less likely to die than white infants (odds ratio [OR] 0.76; 95% confidence interval [CI] 0.62-0.94). However, black infants born at 32-34 weeks (OR 1.64; 95% CI 1.15-2.32) or 35-36 weeks (OR 1.57; 95% CI 1.00-2.24) were more likely to die. Hispanic infants born at 35-36 weeks were less likely to die than white infants (OR 0.66; 95% CI 0.50-0.87). Racial disparities at different GAs were also detected for severe morbidities.

CONCLUSIONS

The impact of race/ethnicity on mortality and severe morbidity varied across GA categories in preterm infants. Disparities persisted even after adjusting for important potential confounders.

Socioeconomic Factors Explain Racial Disparities in Invasive Community-Associated Methicillin-Resistant Staphylococcus aureus Disease Rates

Background

Invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) incidence in the United States is higher among black persons than white persons. We explored the extent to which socioeconomic factors might explain this racial disparity.

Methods

A retrospective cohort was based on the Centers for Disease Control and Prevention's Emerging Infections Program surveillance data for invasive community-associated MRSA cases (isolated from a normally sterile site of an outpatient or on hospital admission day ≤3 in a patient without specified major healthcare exposures) from 2009 to 2011 in 33 counties of 9 states. We used generalized estimating equations to determine census tract-level factors associated with differences in MRSA incidence and inverse odds ratio-weighted mediation analysis to determine the proportion of racial disparity mediated by socioeconomic factors.

Results

Annual invasive community-associated MRSA incidence was 4.59 per 100000 among whites and 7.60 per 100000 among blacks (rate ratio [RR], 1.66; 95% confidence interval [CI], 1.52-1.80). In the mediation analysis, after accounting for census tract-level measures of federally designated medically underserved areas, education, income, housing value, and rural status, 91% of the original racial disparity was explained; no significant association of black race with community-associated MRSA remained (RR, 1.05; 95% CI, .92-1.20).

Conclusions

The racial disparity in invasive community-associated MRSA rates was largely explained by socioeconomic factors. The specific factors that underlie the association between census tract-level socioeconomic measures and MRSA incidence, which may include modifiable social (eg, poverty, crowding) and biological factors (not explored in this analysis), should be elucidated to define strategies for reducing racial disparities in community-associated MRSA rates.

Racial Discrimination and Adverse Birth Outcomes: An Integrative Review

INTRODUCTION

This article presents an integrative review of the literature examining the relationship between racial discrimination and adverse birth outcomes.

METHODS

Searches for research studies published from 2009 to 2015 were conducted using PubMed, CINAHL, Scopus, PsycINFO, Web of Science, and Embase. Articles were assessed for potential inclusion using the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2009 framework.

RESULTS

Fifteen studies met criteria for review. The majority of the studies found a significant relationship between racial discrimination and low birth weight, preterm birth, and small for gestational age. Each of the studies that examined more proximal variables related to birth outcomes such as entry into prenatal care, employment opportunities, neighborhood characteristics, or inflammatory markers found significant associations between the specific variables examined and racial discrimination. Participants in qualitative studies discussed experiences of institutional racism with regard to several components of prenatal care including access and quality of care.

DISCUSSION

Racial discrimination is a significant risk factor for adverse birth outcomes. To best understand the mechanisms by which racial discrimination impacts birth outcomes, and to inform the development of effective interventions that eliminate its harmful effects on health, longitudinal research that incorporates comprehensive measures of racial discrimination is needed. Health care providers must fully acknowledge and address the psychosocial factors that impact health outcomes in minority racial/ethnic women.

Association Between High Ambient Temperature and Risk of Stillbirth in California

Recent studies have linked elevated apparent temperatures with adverse birth outcomes, such as preterm delivery, but other birth outcomes have not been well studied. We examined 8,510 fetal deaths (≥20 weeks' gestation) to estimate their association with mean apparent temperature, a combination of temperature and humidity, during the warm season in California (May-October) from 1999 to 2009. Mothers whose residential zip codes were within 10 km of a meteorological monitor were included. Meteorological data were provided by the California Irrigation Management Information System, the US Environmental Protection Agency, and the National Climatic Data Center, while the California Department of Public Health provided stillbirth data. Using a time-stratified case-crossover study design, we found a 10.4% change (95% confidence interval: 4.4, 16.8) in risk of stillbirth for every 10°F (5.6°C) increase in apparent temperature (cumulative average of lags 2-6 days). Risk varied by maternal race/ethnicity and was greater for younger mothers, less educated mothers, and male fetuses. The highest risks were observed during gestational weeks 20-25 and 31-33. No associations were found during the cold season (November-April), and the observed associations were independent of air pollutants. This study adds to the growing body of literature identifying pregnant women and their fetuses as subgroups vulnerable to heat exposure.

Perinatal Disparities Between American Indians and Alaska Natives and Other US Populations: Comparative Changes in Fetal and First Day Mortality, 1995-2008

To compare fetal and first day outcomes of American Indian and Alaskan Natives (AIAN) with non-AIAN populations. Singleton deliveries to AIAN and non-AIAN populations were selected from live birth-infant death cohort and fetal deaths files from 1995-1998 and 2005-2008. We examined changes over time in maternal characteristics of deliveries and disparities and changes in risks of fetal, first day (<24 h), and cause-specific deaths. We calculated descriptive statistics, odds ratios and confidence intervals, and ratio of odds ratios (RORs) to indicate changes in disparities. Along with black mothers, AIANs exhibited the highest proportion of risk factors including the highest proportion of diabetes in both time periods (4.6 and 6.5 %). Over time, late fetal death for AIANs decreased 17 % (aOR = 0.83, 95 % CI 0.72-0.97), but we noted a 47 % increased risk over time for Hispanics (aOR = 1.47, 95 % CI 1.40-1.55). Our data indicated no change over time among AIANs for first day death. For AIANs compared to whites, increased risks and disparities persisted for mortality due to congenital anomalies (ROR = 1.28, 95 % CI 1.03-1.60). For blacks compared to AIANs, the increased risks of fetal death (2005-2008: aOR = 0.60, 95 % CI 0.53-0.68) persisted. For Hispanics, lower risks compared to AIANs persisted, but protective effect declined over time. Disparities between AIAN and other groups persist, but there is variability by race/ethnicity in improvement of perinatal outcomes over time. Variability in access to care and pregnancy management should be considered in relation to health equity for fetal and early infant deaths.

The role of social determinants in explaining racial/ethnic disparities in perinatal outcomes

In the United States, there continue to be significant racial/ethnic disparities in preterm birth (PTB) rates, infant mortality, and fetal mortality rates. One potential mediator of these disparities is social determinants of health, including individual socioeconomic factors; community factors such as crime, poverty, housing, and the racial/ethnic makeup of the community; and the physical environment. Previous work has identified statistically significant associations between each of these factors and adverse pregnancy outcomes. However, there are recent studies that provide new, innovative insights into this subject, including adding social determinant data to population-based datasets; exploring multiple constructs in their analysis; and examining environmental factors. The objective of this review will be to examine this recent research on the association of each of these sets of social determinants on racial/ethnic disparities PTB, infant mortality, and fetal mortality to highlight potential areas for targeted intervention to reduce these differences.

Morbidity and mortality associated with mode of delivery for breech periviable deliveries

OBJECTIVE

The purpose of this study was to estimate the odds of morbidity and death that are associated with cesarean delivery, compared with vaginal delivery, for breech fetuses who are delivered from 23-24 6/7 weeks' gestational age.

STUDY DESIGN

We conducted a retrospective cohort study of state-level maternal and infant hospital discharge data that were linked to vital statistics for breech deliveries that occurred from 23-24 6/7 weeks' gestation in California, Missouri, and Pennsylvania from 2000-2009 (N = 1854). Analyses were stratified by gestational age (23-23 6/7 vs 24-24 6/7 weeks' gestation).

RESULTS

Cesarean delivery was performed for 46% (335 fetuses) and 77% (856 fetuses) of 23- and 24-week breech fetuses. In multivariable analyses, overall survival was greater for cesarean-born neonates (adjusted odds ratio [AOR], 3.98; 95% confidence interval [CI], 2.24-7.06; AOR, 2.91; 95% CI, 1.76-4.81, respectively). When delivered for nonemergent indications, cesarean-born survivors were more than twice as likely to experience major morbidity (intraventricular hemorrhage, bronchopulmonary dysplasia, necrotizing enterocolitis, asphyxia composite; AOR, 2.83; 95% CI, 1.37-5.84; AOR, 2.07; 95% CI, 1.11-3.86 at 23 and 24 weeks' gestation, respectively). Among intubated neonates, despite a short-term survival advantage, there was no difference in survival to >6-month corrected age (AOR, 1.77; 95% CI, 0.83-3.74; AOR, 1.50; 95% CI, 0.81-2.76, respectively). There was no difference in survival for intubated 23-week neonates who were delivered by cesarean for nonemergent indications or cesarean-born neonates who weighed <500 g.

CONCLUSION

Cesarean delivery increased overall survival and major morbidity for breech periviable neonates. However, among intubated neonates, despite a short-term survival advantage, there was no difference in 6-month survival. Also, cesarean delivery did not increase survival for neonates who weighed <500 g. Patients and providers should discuss explicitly the trade-offs related to neonatal death and morbidity, maternal morbidity, and implications for future pregnancies.

Trends in childbirth before 39 weeks' gestation without medical indication

BACKGROUND

There is increasing attention to labor induction and cesarean delivery occurring at 37 0/7-38 6/7 weeks' gestation (early-term) without medical indication.

OBJECTIVE

To measure prevalence, change over time, patient characteristics, and infant outcomes associated with early-term nonindicated births.

RESEARCH DESIGN AND SUBJECTS

Retrospective analysis using linked hospital discharge and birth certificate data for the 7,296,363 uncomplicated births (>37 0/7 wk' gestation) between 1995 and 2009 in 3 states.

MEASURES

Early-term nonindicated birth is calculated using diagnosis codes and birth certificate records. Secondary outcomes included infant prolonged length of stay and respiratory distress.

RESULTS

Across uncomplicated term births, the early-term nonindicated birth rate was 3.18%. After adjustment, the risk of nonindicated birth before 39 0/7 weeks was 86% higher in 2009 than in 1995 [hazard ratio (HR)=1.86; 95% confidence interval (CI), 1.81-1.90], peaking in 2006 (HR=2.03; P<0.001). Factors independently associated with higher odds included maternal age, higher education levels, private health insurance, and delivering at smaller-volume or nonteaching hospitals. Black women had higher risk of nonindicated cesarean birth (HR=1.29; 95% CI, 1.27-1.32), which was associated with greater odds of prolonged length of stay [adjusted odds ratio (AOR)=1.60; 95% CI, 1.57-1.64] and infant respiratory distress (AOR=2.44; 95% CI, 2.37-2.50) compared with births after 38 6/7 weeks. Early-term nonindicated induction was also associated with comparatively greater odds of prolonged length of stay (AOR=1.20; 95% CI, 1.17-1.23).

CONCLUSIONS

Nearly 4% of all uncomplicated births to term infants occurred before 39 0/7 weeks' gestation without medical indication. These births were associated with adverse infant outcomes.

Instrumental variable methods for causal inference

A goal of many health studies is to determine the causal effect of a treatment or intervention on health outcomes. Often, it is not ethically or practically possible to conduct a perfectly randomized experiment, and instead, an observational study must be used. A major challenge to the validity of observational studies is the possibility of unmeasured confounding (i.e., unmeasured ways in which the treatment and control groups differ before treatment administration, which also affect the outcome). Instrumental variables analysis is a method for controlling for unmeasured confounding. This type of analysis requires the measurement of a valid instrumental variable, which is a variable that (i) is independent of the unmeasured confounding; (ii) affects the treatment; and (iii) affects the outcome only indirectly through its effect on the treatment. This tutorial discusses the types of causal effects that can be estimated by instrumental variables analysis; the assumptions needed for instrumental variables analysis to provide valid estimates of causal effects and sensitivity analysis for those assumptions; methods of estimation of causal effects using instrumental variables; and sources of instrumental variables in health studies.