Chronic Hypertension in Pregnancy and Racial-Ethnic Disparities in Complications

To evaluate whether there are individual- and population-level associations between chronic hypertension and pregnancy complications, and to assess differences across seven racial-ethnic groups. This population-based study used linked vital statistics and hospitalization discharge data from all live and stillbirths in California (2008-2018), Michigan (2008-2020), Oregon (2008-2020), Pennsylvania (2008-2014), and South Carolina (2008-2020). We used multivariable log-binomial regression models to estimate risk ratios (RRs) and population attributable risk (PAR) percentages with 95% CIs for associations between chronic hypertension and several obstetric and neonatal outcomes, selected based on prior evidence and pathologic pathways. We adjusted models for demographic factors (race and ethnicity, payment method, educational attainment), age, body mass index, obstetric history, delivery year, and state, and conducted analyses stratified across seven racial-ethnic groups. The study included 7,955,713 pregnancies, of which 168,972 (2.1%) were complicated by chronic hypertension. Chronic hypertension was associated with several adverse obstetric and neonatal outcomes, with the largest adjusted PAR percentages observed for preeclampsia with severe features or eclampsia (22.4; 95% CI 22.2-22.6), acute renal failure (13.6; 95% CI 12.6-14.6), and pulmonary edema (10.7; 95% CI 8.9-12.6). Estimated RRs overall were similar across racial-ethnic groups, but PAR percentages varied. The adjusted PAR percentages (95% CI) for severe maternal morbidity-a widely used composite of acute severe events-for people who were American Indian or Alaska Native, Asian, Black, Latino, Native Hawaiian or Other Pacific Islander, White, and Multiracial or Other were 5.0 (1.1-8.8), 3.7 (3.0-4.3), 9.0 (8.2-9.8), 3.9 (3.6-4.3), 11.6 (6.4-16.5), 3.2 (2.9-3.5), and 5.5 (4.2-6.9), respectively. Chronic hypertension accounts for a substantial fraction of obstetric and neonatal morbidity and contributes to higher complication rates, particularly for people who are Black or Native Hawaiian or Other Pacific Islander.