Disparities in Patterns of Preterm and Early Term Second Births Among Non-Hispanic Black and White Mothers

Abstract

Background: Early term births (37-38 weeks), like preterm births (< 37 weeks) are associated with increased infant morbidity, mortality, and risk of future preterm births. While racial disparities in preterm births are well documented, longitudinal patterns of early term and preterm births by maternal race remain underexplored.

Objectives: To estimate the likelihood of second births that are preterm or early term, conditional on the gestational age category of the mother's first birth and maternal race.

Methods: This population-based cohort study used linked birth and hospital discharge records for non-Hispanic (NH) Black and White mothers in Georgia with a first and second singleton live birth between 2011 and 2020. We examined the unadjusted distributions of second birth gestational age (< 32, 32-36, 37-38, ≥ 39 weeks) stratified by first birth gestational age category and maternal race. Adjusted relative risk ratios (RRRs) were estimated using multinomial logit models.

Results: NH Black mothers delivered 31,768 births; NH White mothers delivered 58,113. Among mothers with a first preterm birth < 32 weeks, NH Black mothers had a higher likelihood of second births at < 32 (RRR 19.08, 95% CI 14.48, 24.98) than NH White mothers (10.17, 95% CI 7.00, 14.78) and had similar disparities for second births at 32-36 weeks. After early term first births, NH Black mothers had elevated risks of < 32 or 32-36 week births (RRRs 3.53, 95% CI 2.90, 4.30 and 2.88, 95% CI 2.64, 3.13 respectively) versus NH White mothers (1.73, 95% CI 1.41, 2.11 and 2.07, 95% CI 1.92, 2.22). Racial disparities extended to second births following full-term first births and persisted after restricting the sample to non-indicated first births.

Conclusions: NH Black mothers face relatively elevated risks of shortened gestation in subsequent births, regardless of the gestational age of their first birth, including after early term or full-term births.

Keywords: early term birth; preterm birth; previous birth; race disparities; second births; shortened gestational age.