Risk of Adverse Perinatal Outcomes Among African-born Black Women in California, 2011–2020

Abstract

Background: African-born women have a lower risk of preterm birth and small for gestational age (SGA) birth compared to United States (US)-born Black women, however variation by country of origin is overlooked. Additionally, the extent that nativity disparities in adverse perinatal outcomes to Black women are explained by individual-level factors remains unclear. Methods: We conducted a population-based study of non-anomalous singleton live births to US- and African-born Black women in California from 2011-2020 (n=194,320). We used age-adjusted Poisson regression models to estimate risk of preterm birth and SGA, and reported risk ratios (RR) and 95% confidence intervals (CI). Decomposition using Monte Carlo integration of the g-formula computed the percentage of disparities in adverse outcomes between US- and African-born women explained by individual-level factors. Results: Eritrean women (RR 0.4; 95%CI: 0.3, 0.5) had the largest differences in risk of preterm birth and Cameroonian women (RR 0.5; 95% CI: 0.3, 0.6) in SGA birth, compared to US-born Black women. Ghanaian women had smaller differences in risk of preterm birth (RR 0.8; 95%CI: 0.7, 1.0) and SGA (RR 0.9; 95% CI 0.8, 1.1) compared to US-born women. Overall, we estimate that absolute differences in socio-demographic and clinical factors contributed to 32% of nativity-based disparities in the risk of preterm birth and 26% of disparities in SGA. Conclusions: We observed heterogeneity in risk of adverse perinatal outcomes for African- compared to US-born Black women, suggesting that nativity disparities in adverse perinatal outcomes were not fully explained by differences in individual-level factors.