Introduction:Ischemic stroke (IS) is an uncommon, but potentially life-changing, complication of pregnancy. The aim of this study was to analyze the etiology and risk factors of pregnancy-associated IS.Patients and methods:We collected a population-based retrospective cohort of patients diagnosed with IS during pregnancy or puerperium in Finland from 1987 to 2016. These women were identified by linking the Medical Birth Register (MBR) with the Hospital Discharge Register. Three matched controls were selected from MBR for each case. The diagnosis and temporal relationship of IS to pregnancy, and clinical details were verified from patient records.Results:A total of 97 women (median age 30.7 years) were identified as having pregnancy-associated IS. The most common etiologies based on TOAST classification were cardioembolism in 13 (13.4%), other determined in 27 (27.8%) and undetermined in 55 (56.7%) patients. Fifteen patients (15.5%) had embolic strokes of undetermined sources. The most important risk factors were pre-eclampsia, eclampsia, gestational hypertension, and migraine. IS patients had more frequently traditional and pregnancy-related stroke risk factors than the controls (OR 2.38, 95% CI 1.48–3.84) and the risk of IS multiplied with the number of risk factors (4–5 risk factors: OR 14.21, 95% CI 1.12–180.48).Discussion and conclusion:Rare causes and cardioembolism were frequent etiologies for pregnancy-associated IS, but in half of the women, the etiology remained undetermined. The risk of IS increased with the number of risk factors. Surveillance and counseling of pregnant women, especially with multiple risk factors, is crucial for the prevention of pregnancy-associated IS.