BACKGROUND: Pregnancy-associated hemorrhagic stroke is considered a serious complication. Although coagulopathy, pregnancy-induced hypertension, eclampsia, and other systemic complications have been emphasized, pre-existing cerebrovascular diseases (CVDs) have not been fully analyzed. To clarify the role of these vascular lesions more in detail, the Japan Neurosurgical Society conducted a nationwide survey on all the neurosurgical institutes across Japan. METHODS: This 2-year survey focused on hemorrhagic stroke occurring in pregnancy, delivery, and puerperium. Clinical data based on retrospective chart review were obtained through a questionnaire and analyzed according to the time of onset, underlying CVDs, obstetric systemic complications, therapeutic approaches, and maternal and neonatal prognoses. RESULTS: The survey identified 97 hemorrhagic strokes that were associated with pregnancy. Baseline CVDs responsible for hemorrhage were detected in 54 cases (55.7%), among which 47 lesions (87.0%) had been undiagnosed before stroke onset. The detection rate of baseline CVDs before the 32nd week of gestation was significantly higher than that after the 32nd week (90.0% versus 53.3%, P = .0017). Arteriovenous malformations (AVMs) were the most frequent CVDs causing intracranial hemorrhage, occurring at 1.8 times the frequency of ruptured aneurysms during pregnancy. Poor outcomes, including 10 deaths, were seen in 36.1% of the cases despite aggressive treatment. CONCLUSION: Pregnancy-associated hemorrhagic strokes frequently concealed baseline CVDs, especially when they occurred before the 32nd week of gestation. AVMs were the predominant bleeding source. For appropriate treatment, therefore, close examination for cerebral vascular lesions is essential when a pregnancy-associated hemorrhagic stroke is encountered.