Severe maternal morbidity and mortality across subtypes of hypertensive disorders in pregnancy

Hypertensive disorders in pregnancy (HDP) are increasingly common in the United States and encompass a spectrum of diagnoses, yet the distinct risk profiles of HDP subtypes remain poorly defined.

To assess the risk of severe maternal morbidity (SMM) and mortality among patients with HDP.

This repeated cross-sectional study analyzed U.S. delivery hospitalizations using the 2015-2021 National Inpatient Sample. Patients were identified as having HDP and adverse outcomes using International Classification of Diseases, Tenth Revision (ICD-10) codes. HDP subtypes were classified as chronic hypertension, gestational hypertension, preeclampsia without severe features, preeclampsia with severe features, superimposed preeclampsia, HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome, and eclampsia. The primary outcomes were SMM and mortality. Temporal trends in the diagnosis of HDP were analyzed using joinpoint regression to estimate the average annual percent change (AAPC). Adjusted multivariate logistic regression and population-attributable fractions (aPAF) were used to examine the association between HDP and SMM outcomes. Additional subgroup analysis were performed to estimate SMM risk by race and ethnicity.

Among the 22,554,997 parturients in this study, 3,423,849 (15.2%) had HDP. From 2015 to 2021, the rate of HDP increased from 12.0% to 18.8% (AAPC +7.8%, 95% CI 7.6-8.0). Compared to those without, HDP was associated with a higher risk of SMM (0.5% vs 2.0%; adjusted odds ratio [aOR] 3.04, 95% CI 2.96-3.12) and maternal death (0.7 vs 2.5 per 10,000 delivery hospitalizations; aOR 2.41, 95% CI 1.97-2.95). Among SMM indicators, those with HDP were at highest risk for cardiovascular (aOR 5.14, 95% CI 4.81-5.49) and renal (aOR 8.30, 95% CI 7.82-8.80) SMM. Among HDP subtypes, HELLP syndrome and eclampsia were associated with high risk for all SMM subcategories (aOR 1.92-158.59). Overall, 26.6% (aPAF, 95% CI 25.9-27.3) of hospitalizations with SMM and 22.3% (aPAF, 95% CI 16.2-28.0) of hospitalizations with maternal death were attributable to HDP. Asian or Pacific Islander patients had the greatest SMM risk (aOR 3.47; 95% CI 3.15-3.83) among racial and ethnic groups. The aPAF between HDP and SMM (34.8%, 95% CI 33.2-36.4) was greater among non-Hispanic Black patients compared to other racial and ethnic groups.

HDP was significantly associated with an increased risk of SMM and mortality, with eclampsia and HELLP syndrome posing the highest risks.