Allostatic Load Mediates Associations Between Race and Ethnicity and Hypertensive Disorders of Pregnancy.

Objective: To evaluate whether chronic stress exposure, measured by allostatic load (a biological measure of chronic stress embodiment, including stressors exacerbated by structural inequities [eg, structural racism]) and patient-reported perceived stress in the first trimester of pregnancy, mediates the association between self-identified race and ethnicity and hypertensive disorders of pregnancy (HDP).

Methods: This was a secondary analysis of data from nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be), a large prospective cohort study. We evaluated self-identified race and ethnicity as an independent variable (non-Hispanic Black, Hispanic, Asian, non-Hispanic White), and our outcome of interest was HDP (ie, gestational hypertension, preeclampsia or eclampsia). Allostatic load was operationalized with regression- and count-based approaches. Perceived stress was collected with the Cohen perceived stress scale. We investigated allostatic load and perceived stress and used causal mediation analyses with a counterfactual approach to evaluate whether they mediated the association between self-identified race and ethnicity and HDP, adjusting for age and tobacco use. Mediation analyses were conducted for each minoritized racial and ethnic group compared with non-Hispanic White participants.

Results: The sample included 645 participants who developed HDP and 2,438 participants without HDP or other adverse pregnancy outcome. Allostatic load and perceived stress varied by race and ethnicity; HDP varied by allostatic load but not perceived stress. Allostatic load was a partial mediator exclusively in the comparison of non-Hispanic Black and non-Hispanic White participants (0.027, 95% CI, 0.013-0.040, P<.001; 28.9%). Perceived stress was not a significant mediator.

Conclusion: First-trimester allostatic load mediated the association between self-identified race and ethnicity and HDP for non-Hispanic Black and non-Hispanic White participants. This mediation effect was not observed in other racial and ethnic comparisons. These results demonstrate a physiologic pathway through which racism may contribute to adverse pregnancy outcomes and suggest that interventions targeting allostatic load reduction could help address racial and ethnic disparities in HDP.