Background: Non-Hispanic (NH) Black pregnant individuals experience disproportionately higher rates and more severe complications of hypertensive disorders of pregnancy (HDPs) compared to their  NH White counterparts. Limited research has explored whether factors such as social support modify these disparities. This study examined whether social support modified the relationship between race and HDP.

Methods: Included were 6,289 nulliparous individuals with singleton pregnancies who self-identified as NH Black or NH White. Race (a proxy for racism) was the primary exposure. Self-reported perceived social support (Multidimensional Scale of Perceived Social Support at visit 1 (first trimester) was the effect measure modifier of interest and dichotomized at the 75th percentile (reference: high). Outcomes, preeclampsia (PE) and new-onset gestational hypertension (GHTN), were analyzed separately. Effect modification on the multiplicative scale was assessed using multivariable logistic regression.

Results: NH Black participants had higher rates of PE (12.3% vs. 8.7%; p < 0.001) and were more likely to report low perceived social support (77.4% vs. 67.9%; p < 0.001) than NH White participants. In adjusted models, the joint effects of NH Black race and low perceived social support were associated with nearly twice the odds of PE compared with NH White participants with high social support (OR = 1.81; 95% CI: 1.30–2.52). No effect modification was observed for GHTN.

Conclusion: The joint effects of NH Black race and low perceived social support were associated with increased odds of PE, but not GHTN. These findings suggest that interventions incorporating social support during pregnancy may help reduce the risk of PE in this high-risk group.