(419) Social Vulnerability and Racial Disparities in Preterm Birth: A National Cohort Study

To evaluate the association between county-level social vulnerability and preterm birth, and assess whether racial disparities vary across levels of social vulnerability.


Study Design:

This cross-sectional study used restricted Centers for Disease Control and Prevention natality data from 2016–2021. We included Black or White individuals aged 15–44 years with singleton pregnancies across 3,114 U.S. counties. Participants were grouped into quartiles based on the county-level Social Vulnerability Index (SVI) (Figure 1). The primary outcome was preterm birth, defined as delivery before 37 weeks. Secondary outcomes included small for gestational age (SGA) (birth weight < 10th percentile), pregnancy-related hypertension (HTN), and no prenatal care. We used mixed-effects generalized linear models with Poisson distribution to calculate average marginal effects (AMEs) with 95% confidence intervals (95% CI), adjusted for confounders. Difference-in-differences (DID) was calculated for the difference in Black-White disparity across SVI quartiles, with quartile 1 as a reference.


Results:

A total of 2,198,560 individuals were included: 368,256 in quartile 1, 554,767 in quartile 2, 632,717 in quartile 3, and 642,820 in quartile 4. Black individuals had higher adjusted rates of preterm birth than White individuals in all quartiles. Black and White preterm birth rates were 12.1% vs. 9.6% (AME 2.5%, 95% CI 1.9–3.0) in quartile 1; 13.2% vs. 9.7% (AME 3.5%; 95% CI 3.1-3.9) in quartile 2, 13.6% vs. 10.1% (AME 3.5; 95% CI 3.1-3.8) in quartile 3; and 14.6% vs. 10.4% (AME 4.24%, 95% CI 3.89–4.58) in quartile 4 (Table 1). The DID as a disparity indicator increased as social vulnerability increased; DID was statistically significant in quartiles 2-4 compared to quartile 1. Secondary outcomes had similar trends, with widening disparities in pregnancy-related HTN, SGA, and prenatal care.


Conclusion:

Increasing social vulnerability is associated with widening racial disparities in preterm birth and other adverse pregnancy outcomes. These findings underscore the need to address community-level influences on perinatal inequities.