BackgroundPregnant women may have an increased risk of stroke compared with nonpregnant women of similar age, but the magnitude and the timing of such risk are unclear. We examined the risk of a first stroke event in women of childbearing age and compared the risk during pregnancy and in the early postpartum period with the background risk outside these periods.Methods and ResultsWe conducted an open cohort study of 2 046 048 women aged 15 to 49 years between April 1, 1997, and March 31, 2014, using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care records in England. Risk of first stroke was assessed by calculating the incidence rate of stroke in antepartum, peripartum (2 days before until 1 day after delivery), and early (first 6 weeks) and late (second 6 weeks) postpartum periods compared with nonpregnant time using a Poisson regression model with adjustment for maternal age, socioeconomic group, and calendar time. A total of 2511 women had a first stroke. The incidence rate of stroke was 25.0 per 100 000 person‐years (95% CI 24.0–26.0) in nonpregnant time. The rate was lower antepartum (10.7 per 100 000 person‐years, 95% CI 7.6–15.1) but 9‐fold higher peripartum (161.1 per 100 000 person‐years, 95% CI 80.6–322.1) and 3‐fold higher early postpartum (47.1 per 100 000 person‐years, 95% CI 31.3–70.9). Rates of ischemic and hemorrhagic stroke both increased peripartum and early postpartum.ConclusionsAlthough the absolute risk of first stroke is low in women of childbearing age, healthcare professionals should be aware of a considerable increase in relative risk during the peripartum and early postpartum periods.