The incidence of first stroke in and around pregnancy: A population-based cohort study from Sweden

Introduction:Research has suggested that delivery is associated with an increased risk of stroke in women; however, there is a lack of contemporary estimates on the incidence of stroke in and after pregnancy compared with the baseline risk in women of childbearing age in Sweden.Patients and methods:All women aged 15–49 years with live births/stillbirths in 1992–2011 were identified from the Swedish Medical Birth Registry linked with the National Patient Registry. First stroke during the study period was identified. Incidence rates per 100,000 person-years and adjusted incidence rate ratios (IRRs) were calculated for antepartum, peripartum and early and late postpartum periods, compared with all other available follow-up time (time before pregnancy and after postpartum) using Poisson regression adjusted for maternal age, education attainment and calendar time.Results:Of 1,124,541 women, 3094 had a first incident stroke (331 occurred during pregnancy or first 12 weeks postpartum), about half having ischaemic stroke. The incidence was 15.0 per 100,000 person-years (95% confidence interval 14.5–15.6) in non-pregnant time. The incidence was lower antepartum (7.3/100,000 person-years, 6.0–8.9; adjusted IRR = 0.7, 0.5–0.8) but higher peripartum (314.4/100,000 person-years, 247.5–399.5; adjusted IRR = 27.3, 21.4–34.9) and early postpartum (64.0/100,000 person-years, 54.1–75.7; adjusted IRR = 5.5, 4.6–6.6). The increased risk in peripartum was more evident for intracerebral haemorrhage than other types of stroke.Conclusion:Overall risk of stroke was low in women of childbearing age, but stroke risk peaks in the peripartum and early postpartum periods. Future work should address factors that contribute to this increased risk in order to develop approaches to attenuate risk