Independent and interactive effects of race and insurance on preterm birth risk

OBJECTIVE: To assess racial and ethnic disparities in preterm delivery in the US and evaluate whether insurance type modifies these associations. METHODS: We analyzed National Center for Health Statistics natality data (2018-2024) comprising 24,918,700 singleton live births. Preterm delivery was defined as birth before 37 completed weeks of gestation. Multivariable logistic regression with robust variance was used to estimate adjusted odds ratios, predicted probabilities, and absolute risk differences across race/ethnicity and insurance categories, adjusting for maternal sociodemographic, clinical, and obstetric factors. RESULTS: Overall, 2,134,329 of 24,918,700 singleton live births (8.6%) were preterm during the study period, with annual rates remaining stable between 8.23% and 8.75%. In multivariable-adjusted analyses, non-Hispanic Black women had the highest odds of preterm delivery (adjusted odds ratio [aOR], 1.40; 95% confidence interval [CI]: 1.39-1.40), compared with non-Hispanic White women. Racial and ethnic disparities persisted across all insurance strata; among uninsured women, non-Hispanic Black women had the largest absolute risk difference relative to non-Hispanic White women (5.74 percentage points; 95% CI: 5.52-5.96), which was attenuated but remained significant among Medicaid (2.38 percentage points; 95% CI: 2.33-2.43) and privately insured women (2.66 percentage points; 95% CI: 2.60-2.73). Insurance coverage attenuated but did not eliminate these disparities. CONCLUSION: Racial and ethnic disparities in preterm delivery persist in the US despite insurance coverage, underscoring the need for policies that address both healthcare access and structural determinants of maternal health.