Racial disparity in previable birth.

Extremely preterm birth of a live newborn before the limit of viability is rare but contributes uniformly to the infant mortality rate because essentially all cases result in neonatal death. The objective of the study was to quantify racial differences in previable birth and their contribution to infant mortality and to estimate the relative influence of factors associated with live birth occurring before the threshold of viability. This was a population-based retrospective cohort of all live births in Ohio over a 7 year period, 2006-2012. Demographic, pregnancy, and delivery characteristics of previable live births at 16 0/7 to 22 6/7 weeks of gestation were compared with a referent group of live births at 37 0/7 to 42 6/7 weeks. Rates of birth at each week of gestation were compared between black and white mothers, and relative risk ratios were calculated. Logistic regression estimated the relative risk of factors associated with previable birth, with adjustment for concomitant risk factors. Of 1,034,552 live births in Ohio during the study period, 2607 (0.25% of all live births) occurred during the previable period of 16-22 weeks. There is a significant racial disparity in the rate and relative risk of previable birth, with a 3- to 6-fold relative risk increase in black mothers at each week of previable gestational age. The incidence of previable birth for white mothers was 1.8 per 1000 and for black mothers, 6.9 per 1000. Factors most strongly associated with previable birth, presented as adjusted relative risk ratio (95% confidence interval [CI]), were maternal characteristics of black race adjusted relative risk 2.9 (95% CI, 2.6-3.2), age ≥ 35 years 1.3 (95% CI, 1.1-1.6), and unmarried 2.1 (95% CI, 1.8-2.3); fetal characteristics including congenital anomaly, 5.4 (95% CI, 3.4-8.1) and genetic disorder, 5.1 (95% CI, 2.5-10.1); and pregnancy characteristics including prior preterm birth 4.4 (95% CI, 3.7-5.2) and multifetal gestation, twin, 16.9 (95% CI, 14.4-19.8) or triplet, 65.4 (95% CI, 32.9-130.2). The majority, 80%, of previable births (16-22 weeks) were spontaneous in nature, compared with 73% in early preterm births (23-33 weeks), 72% in late preterm births (34-36 weeks), and 65% of term births (37-42 weeks) (P < .001). Previable births constituted approximately 28% of total infant mortalities in white newborns and 45% of infant mortalities in black infants in Ohio during the study period. There is a significant racial disparity in previable preterm births, with black mothers incurring a 3- to 6-fold increased relative risk compared with white mothers, most of which are spontaneous in nature. This may explain much of the racial disparity in infant mortality because all live-born previable preterm births result in death. Focused efforts on the prevention of spontaneous previable preterm birth may help to reduce the racial disparity in infant mortality.

DeFranco EA ，Hall ES ，Muglia LJ 《-》

Contribution of previable births to infant mortality rate racial disparity in the United States.

Lee M ，Hall ES ，DeFranco E 《-》

Maternal race and intergenerational preterm birth recurrence.

Preterm birth is a complex disorder with a heritable genetic component. Studies of primarily White women born preterm show that they have an increased risk of subsequently delivering preterm. This risk of intergenerational preterm birth is poorly defined among Black women. Our objective was to evaluate and compare intergenerational preterm birth risk among non-Hispanic Black and non-Hispanic White mothers. This was a population-based retrospective cohort study, using the Virginia Intergenerational Linked Birth File. All non-Hispanic Black and non-Hispanic White mothers born in Virginia 1960 through 1996 who delivered their first live-born, nonanomalous, singleton infant ≥20 weeks from 2005 through 2009 were included. We assessed the overall gestational age distribution between non-Hispanic Black and White mothers born term and preterm (<37 weeks) and their infants born term and preterm (<37 weeks) using Cox regression and Kaplan-Meier survivor functions. Mothers were grouped by maternal gestational age at delivery (term, ≥37 completed weeks; late preterm birth, 34-36 weeks; and early preterm birth, <34 weeks). The primary outcomes were: (1) preterm birth among all eligible births; and (2) suspected spontaneous preterm birth among births to women with medical complications (eg, diabetes, hypertension, preeclampsia and thus higher risk for a medically indicated preterm birth). Multivariable logistic regression was used to estimate odds of preterm birth and spontaneous preterm birth by maternal race and maternal gestational age after adjusting for confounders including maternal education, maternal age, smoking, drug/alcohol use, and infant gender. Of 173,822 deliveries captured in the intergenerational birth cohort, 71,676 (41.2%) women met inclusion criteria for this study. Of the entire cohort, 30.0% (n = 21,467) were non-Hispanic Black and 70.0% were non-Hispanic White mothers. Compared to non-Hispanic White mothers, non-Hispanic Black mothers were more likely to have been born late preterm (6.8% vs 3.7%) or early preterm (2.8 vs 1.0%), P < .001. Non-Hispanic White mothers who were born (early or late) preterm were not at an increased risk of early or late preterm delivery compared to non-Hispanic White mothers born term. The risk of early preterm birth was most pronounced for Black mothers who were born early preterm (adjusted odds ratio, 3.26; 95% confidence interval, 1.77-6.02) compared to non-Hispanic White mothers. We found an intergenerational effect of preterm birth among non-Hispanic Black mothers but not non-Hispanic White mothers. Black mothers born <34 weeks carry the highest risk of delivering their first child very preterm. Future studies should elucidate the underlying pathways leading to this racial disparity.

Smid MC ，Lee JH ，Grant JH ，Miles G ，Stoddard GJ ，Chapman DA ，Manuck TA ... -  《-》

Mode of Delivery in Previable Births.

Preterm birth before 23 weeks of gestation typically results in neonatal death (5% survival). Society for Maternal-Fetal Medicine and American College of Obstetricians and Gynecologists published consensus guidelines recommending cesarean delivery (CD) not be performed for fetal indications between 20 and 226/7 weeks given the lack of proven benefit. We sought to quantify the previable CD rate and identify characteristics associated with previable CD. We performed a population-based retrospective cohort study of all live births in Ohio (2006-2015). Frequency of previable CD was stratified by week of gestation, defined as delivery between 16 and < 23 weeks of gestation. Maternal, obstetric, and neonatal characteristics were compared between women who underwent vaginal delivery versus CD. Multivariable logistic regression estimated the relative influence of maternal and fetal factors on the outcome of CD among previable live births. Of 1,463,506 live births in Ohio during the 10-year study period, 2,865 births (0.2%) occurred during the previable period of 16 to 22 weeks. Nearly 1 in 10 live births at less than 23 weeks was delivered by cesarean (n = 273/2,865), CD rate 9.5% (95% confidence interval, 8.5-10.7). At 16 to 22 weeks of gestation, the CD rates were 0, 5.5, 7.6, 3.5, 5.4, 10.1, and 15.1%, respectively. Factors associated with CD included increasing parity, increasing birth weight, maternal corticosteroid administration, and fetal malpresentation. Previable neonates born by CD were more likely to be admitted to the NICU, receive ventilator support, and more likely to be living at the time of birth certificate filing. Nearly 1 out of 10 births during the previable period was delivered via cesarean. Factors associated with previable CD suggest intent for neonatal interventions, such as NICU admission and supportive therapies. Our findings support that education and adherence with guidelines for care of previable births are a potential area of focus for perinatal quality improvement efforts.

Rossi RM ，DeFranco EA 《-》

Contribution of previable live births to disparity in infant mortality of US-born Puerto Ricans compared with infants of other Hispanic origins.

Although US-born Hispanics experience infant mortality rates (IMRs) which are lower than the national rate, within the Hispanic population, infants of Puerto Rican origin experience higher IMRs than other Hispanics. We aimed to describe the contribution of deaths among previable live-born infants to disparity in IMRs comparing Puerto Rican infants to infants of other Hispanic origins. Retrospective, descriptive analysis. We analyzed data from the Centers for Disease Control and Prevention (CDC) WONDER online database representing linked US live births and infant deaths from 2005 to 2014. Data were stratified by race and ethnicity as well as by Puerto Rican and non-Puerto Rican Hispanic origin. Live births <23 weeks of gestation were classified as previable. Ten-year IMRs were calculated as the number of deaths divided by the number of live births for each group over the entire decade. Puerto Rican IMR of 7.34 (per 1000 live births) was higher than the US rate of 6.34 as well as the non-Puerto Rican Hispanic IMR of 5.15. Approximately 22% of US deaths were attributable to previable live births compared with 27% among Puerto Ricans and 20% among non-Puerto Rican Hispanics. The contribution to IMR of previable births among Puerto Ricans measuring 1.96 per 1000 total live births was 42% higher than the US rate of 1.38 and 90% higher than the non-Puerto Rican Hispanic rate of 1.03. Further research is needed to develop interventions to reduce disparity in previable birth rates, particularly among infants of Puerto Rican origin.

Hall ES ，Lee M ，DeFranco EA 《-》