To examine the effect of the number of pregnancies on the subsequent risk for stroke and stroke subtypes.
Prospective cohort study.
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.
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).
The number of pregnancies may influence the risk for stroke, particularly cerebral infarction, in women.