Risk of ischemic stroke among users of the oral contraceptive pill: The Melbourne Risk Factor Study (MERFS) Group.

BACKGROUND AND PURPOSE: Use of oral contraceptives has increased, and there is uncertainty about the stroke risk associated with their use. Our aim was to investigate this issue. METHODS: Using case-control techniques, we identified consecutive women with ischemic stroke from 4 Melbourne hospitals. All patients were between 15 and 55 years of age and had no prior stroke. Neighborhood-based control subjects were individually age-matched (+/-5 years) and geographically matched to subject cases. A questionnaire administered to participants elicited information about prior exposure to various potential risk factors, including the oral contraceptive pill (OCP). RESULTS: We included 234 cases and 234 controls (mean age, 42 years). Compared with noncurrent use, current use of the OCP, in doses of 20 cigarettes per day (OR, 3.68; 95% CI, 1.22 to 11.09). CONCLUSIONS: There was no evidence for an association between ischemic stroke and use of the OCP in low doses (