To better characterize postpartum stroke risk associated with hypertensive disorders of pregnancy (HDP) subtypes using the more detailed coding of International Classification of Diseases, Tenth Revision, Clinical Modification.

While HDP are clear risk factors for peripartum stroke morbidity and mortality, there is significant variation in estimated risk among subtypes due to small sample sizes, misclassification, and clinical heterogeneity.

We conducted a retrospective cohort study using the Nationwide Readmissions Database from 2016-2022 to investigate postpartum stroke risks among females age 18-55 diagnosed with HDP during pregnancy. Exposure variables comprised HDP subtypes, and the primary outcome was stroke within 90 days of delivery discharge. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for the associations between HDP and risk of stroke and were adjusted for cardiovascular and obstetric risk factors.

A total of 8,660,971 weighted deliveries were included in the study period, among which 2,019 females (0.02%) experienced a stroke. A diagnosis of HDP significantly increased adjusted and unadjusted hazard rates of stroke in superimposed preeclampsia (HR 2.77; 95% CI 2.00–3.83), severe preeclampsia (HR 1.96; 95% CI 1.52–2.54), and Hemolysis, Elevated Liver Enzymes, and Low Platelets (HELLP) syndrome (HR 2.09; 95% CI 1.17–3.72). When stratified by stroke type, superimposed preeclampsia and severe preeclampsia were associated with increased ischemic (HR 3.86; 95% CI: 2.53–5.89 and HR 2.49; 95% CI 1.76 –3.51, respectively), and hemorrhagic (HR 1.76; 95% CI 1.07–2.93 and HR 1.49; 95% CI 1.03–2.14 respectively) stroke rates. HELLP syndrome was associated with increased ischemic stroke hazard (HR 3.56; 95% CI 1.88–6.73).

Multiple HDP subtypes including HELLP syndrome were associated with increased risk of stroke in the postpartum period, though small sample sizes continue to limit extensive subtype analyses. Further investigation is required to better understand the clinical and pathophysiological variability in HDP subtypes.