Number of pregnancies and risk for stroke and stroke subtypes

Objective: To examine the effect of the number of pregnancies on the subsequent risk for stroke and stroke subtypes. Design: Prospective cohort study. Participants: National cohort of 3852 women aged 45 to 74 years who participated in the first National Health and Nutrition Examination Survey Epidemiology Follow-up Study. Main Outcome Measures: Stroke, cerebral infarction, and intracerebral hemorrhage during a 20-year follow-up period. Results: After adjusting for differences in age, women with 6 or more pregnancies were at an increased risk for any type of stroke (relative risk [RR]=1.7; 95% confidence interval [CI], 1.2-2.3) and cerebral infarction (RR= 1.6; 95% CI, 1.2-2.3). Adjustment for stroke risk factors explained some but not all of the risk associated with pregnancy (RR=1.3; 95% CI, 0.9-1.9 for all stroke, and RR =1.3; 95% CI, 0.9-1.9 for cerebral infarction). The rate of intracerebral hemorrhage was 3-fold higher among women who had been pregnant when compared with nulligravida women; however, this finding did not reach statistical significance possibly because of the small number of intracerebral hemorrhages (n=33). Conclusion: The number of pregnancies may influence the risk for stroke, particularly cerebral infarction, in women.