Stroke in Pregnancy and Puerperium: Validated Incidence Trends With Risk Factor Analysis in Finland 1987-2016.

OBJECTIVE:To investigate whether previously reported increasing incidence of pregnancy-associated stroke (PAS) is observed in chart-validated register data in Finland. In an exploratory analysis, we studied risk factors for PAS. METHODS:We performed a retrospective population-based cohort study and nested case-control study in Finland from 1987 to 2016. The Medical Birth Register (MBR) was linked to the Hospital Discharge Register to identify women with incident stroke (ischemic stroke, cerebral venous thrombosis, intracerebral or subarachnoid hemorrhage) during pregnancy or puerperium. Cases were verified from patient records. Incidence of PAS over the study period in 5-year age groups and pregnancy/postpartum period was calculated per number of deliveries. Three matched controls were selected for each case from MBR to compare risk factors. RESULTS:After chart review, 29.6% (257 of 868) of cases were PAS. The incidence of PAS was 14.5 (95% confidence interval [CI] 12.8-16.3) per 100,000 deliveries. Incidence increased from 11.1 to 25.2 per 100,000 deliveries from 1987 to 1991 to 2012 to 2016 (p < 0.0001). Incidence increased by age from 9.8 to 29.9 per 100,000 deliveries from 20 to 24 years to >40 years of age (p < 0.0001). During the early postpartum period, incidence was 5-fold greater compared to the first trimester. Maternal mortality was 6.6%. In the multivariable-adjusted model, smoking beyond 12 gestational weeks (odds ratio [OR] 1.8, 95% CI 1.2-2.7), migraine (OR 16.3, 95% CI 5.3-49.8), and hypertensive disorders of pregnancy (OR 4.0, 95% CI 2.5-6.3) were the most important risk factors for PAS. CONCLUSION:PAS incidence is increasing, stressing the importance of careful pregnancy surveillance and risk factor management, particularly in older expectant mothers and extending to puerperium. CLASSIFICATION OF EVIDENCE:This study provides Class III evidence that smoking beyond 12 gestational weeks, migraine, and hypertensive disorders of pregnancy are associated with an increased risk of PAS.