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

Background: African-born women have a lower risk of preterm birth and small for gestational age (SGA) birth compared with United States-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 nonanomalous singleton live births to United States-and African-born Black women in California from 2011 to 2020 (n = 194,320). We used age-Adjusted Poisson regression models to estimate the 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 United States-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 with United States-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 with United States-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 with United States-born Black women, suggesting that nativity disparities in adverse perinatal outcomes were not fully explained by differences in individual-level factors.