Association Between the Social Vulnerability Index and Adverse Pregnancy Outcomes

To assess the association between the Social Vulnerability Index (SVI) and racial disparities in pregnancy outcomes across U.S. counties and to quantify these racial disparities.

This was a cross-sectional study using restricted Centers for Disease Control and Prevention data sets, including natality data sets, fetal death data sets, and all-cause mortality data sets from 2016 to 2021. We limited analyses to Black or White individuals aged 15-44 years from 3,114 U.S. counties. Participants were categorized into quartiles based on county-level SVI. The primary outcome was maternal mortality rate while pregnant or within 42 days of the end of pregnancy, and secondary outcomes were pregnancy-related mortality while pregnant or within 365 days of the end of pregnancy, stillbirth, and preterm birth. Mixed-effect generalized linear models with negative binomial distribution were used to quantify disparities, using difference-in-difference analysis to measure the difference in outcomes between Black and White individuals across different levels of social vulnerability (first quartile as referent).

A total of 20,189,328 individuals were included, distributed across SVI quartiles as follows: first quartile 2,558,131, second quartile 4,945,774, third quartile 6,827,503, and fourth quartile 5,857,920. Black individuals experienced significantly higher rates of maternal mortality, pregnancy-related mortality, stillbirth, and preterm birth compared with White individuals regardless of SVI quartiles. Difference-in-difference analyses demonstrated that disparities in maternal mortality rate were significantly larger in the second, third, and fourth quartiles compared with the first quartile (difference-in-difference 14.22 [95% CI, 2.11-26.33], 12.53 [95% CI, 1.26-23.81], and 18.82 [95% CI, 6.67-30.98], respectively). A worsening disparity in pregnancy-related mortality was observed in the fourth quartile, whereas disparities in stillbirth and preterm birth did not show significant differences across SVI quartiles.

Racial disparities in maternal mortality intensified in counties with higher social vulnerability. These findings underscore the need for targeted interventions to address social determinants of health.