Abstract DP151: Subarachnoid Hemorrhage and Cerebral Aneurysm in Pregnancy and Puerperium

Background: The management of unruptured cerebral aneurysms (UCA) during pregnancy is complex, and data on associated subarachnoid hemorrhage (SAH) risk are limited. This study aimed to compare the incidence of SAH during pregnancy and the postpartum period in women with and without UCA, and to assess maternal and fetal outcomes. Methods: We conducted a retrospective cohort study using the COSMOS EPIC database, including pregnancies delivered between January 1, 2016, and January 1, 2024. UCAs and SAH events were identified via ICD-10 codes, with SAH defined as any diagnosis from estimated pregnancy start date to six weeks postpartum. Baseline characteristics were compared using chi-square, t-tests, or Wilcoxon rank-sum tests. Multivariable logistic regression adjusted for clinical covariates evaluated associations between UCA, SAH, and mortality. Propensity score matching (1:1 nearest neighbor, caliper 0.2) balanced baseline variables. Results: Of 5,404,933 pregnancies, 2,770 (0.05%) had a UCA. SAH incidence was significantly higher in the UCA group compared to controls (1.7% vs. 0.008%, p<0.001), predominantly in the third trimester or postpartum. UCAs were strongly associated with SAH (OR 151; 95% CI: 113–203) and mortality (OR 7.71; 95% CI: 3.11–19.11). In 2,542 matched pairs, SAH risk remained higher in the UCA group (1.7% vs. <0.39%, p<0.001), though the mortality association was no longer significant. Fetal and neonatal demise rates were similar between groups. Conclusion: Pregnant patients with UCA face a markedly higher risk of SAH, especially in late pregnancy and postpartum, although the absolute risk after aneurysm diagnosis remains low. These findings emphasize the importance of individualized risk assessment and multidisciplinary management. Further prospective studies are needed to validate these findings.