Work

Association between hypertensive disorders of pregnancy and severe maternal morbidity

Year: 2026

Type: article

Abstract: Background Hypertensive disorders of pregnancy (HDP) are major contributors to both short- and long-term morbidity. Among the adverse outcomes associated with HDP is severe maternal morbidity (SMM). 1–4 Although the various HDP subtypes differ in their timing of onset, clinical presentation, and severity, little is known about how this heterogeneity is associated with the risk of SMM. This study examines the association between subtypes of HDP and SMM. Study Design We examined hospital administrative data for pregnancies resulting in live or stillbirth ≥20 weeks' gestation at the Prisma Health Midlands and Upstate facilities in South Carolina from 2016 to 2024 (n = 96,161). We compared individuals with no hypertensive disorder vs. those with chronic hypertension with superimposed pre-eclampsia with or without severe features or with unspecified severity, chronic hypertension without superimposed pre-eclampsia, pre-eclampsia with and without severe features or with unspecified severity, and gestational hypertension. HDP were defined using International Classification of Disease codes. 5 HDP were classified into mutually exclusive groups based on the highest severity level reached during the pregnancy. Adjusted Poisson regression models with robust error variance were used to determine the association between each HDP and non-transfusion SMM as defined by the Centers for Disease Control, as well as SMM including blood transfusions of ≥1200 mL. The primary adjusted models included maternal race/ethnicity, parity, smoking, marital status, insurance, plurality, and preexisting diabetes mellitus, and secondary adjusted models included maternal race/ethnicity, parity, smoking, marital status, insurance, and comorbidity index score as defined by the California Maternal Quality Care Collaborative. Results Of 96,161 birthing individuals, 27,460 (28.6%) had HDP. HDP were more prevalent among Black birthing individuals, as well as those who smoked, were obese, delivered by cesarean, were unmarried, or had public insurance . Most comorbid conditions were more prevalent among individuals with HDP compared with those without and SMM indicators varied by HDP type. All HDP were associated with increased risk of non-transfusion SMM [chronic hypertension with superimposed pre-eclampsia with severe features adjusted risk ratio (aRR): 9.75 (95% CI: 8.04-11.83), chronic hypertension with superimposed pre-eclampsia without severe features aRR: 4.45 (95% CI: 2.30-8.59), chronic hypertension with pre-eclampsia of unspecified severity aRR: 5.32 (95% CI: 4.36-6.48), chronic hypertension without pre-eclampsia aRR: 2.20 (95% CI: 1.67-2.90), pre-eclampsia with severe features aRR: 6.24 (95% CI: 5.44-7.16), pre-eclampsia without severe features aRR: 3.57 (95% CI: 2.67-4.77), pre-eclampsia of unspecified severity aRR: 3.49 (95% CI: 2.73-4.46), gestational hypertension aRR: 1.72 (95% CI: 1.46-2.02)]. Results were similar for SMM including blood transfusions of ≥1200 mL. When the comorbidity index score was included, most risk estimates remained elevated but were attenuated (Table) . Conclusion In this large cohort, all HDP examined individually and stratified by severity level, were associated with increased SMM risk. Chronic hypertension with superimposed pre-eclampsia with severe features, followed by pre-eclampsia with severe features had the greatest SMM risk. Analyses that treat hypertensive disorders as a composite exposure or fail to account for severity may mask important differences in risk. These findings have direct implications for patient counseling, clinical decision-making, and risk stratification. Strengths of this study include the classification of HDP by both type and severity. Limitations include reliance on hospital administrative data for HDP classification, which may introduce misclassification bias; some missing maternal BMI data, which may lead to underestimation of comorbidity index scores; lack of postpartum data; and not accounting for antihypertensive treatments, which may be associated with SMM outcomes.

Source: American Journal of Obstetrics and Gynecology

DOI: 10.1016/j.ajog.2026.04.016

Authors: Marion E. Granger Howard, Berry A. Campbell, Nansi S. Boghossian

Institution: University of South Carolina

Language: English

Topic: Pregnancy and preeclampsia studies

Subfield: Obstetrics and Gynecology

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $5,410