PIP: At least 14 retrospective studies and two prospective cohort studies have examined the influence of oral contraceptive (OC) use on the risk of cerebral thromboembolism. Although these studies generally reported significantly increased relative risks for developing cerebral thromboembolism among OC users, most were conducted during a period when high-dose OCs with more than 50 mcg of estrogen were widely prescribed. A 1990 Danish case-control study found that the thromboembolism risk was dose-dependent. OCs containing 30-40 mcg of estrogen implied an odds ratio of 1.8 (95% confidence interval (CI), 1.1-2.9) compared with 2.9 (95% CI, 1.6-5.4) for OCs containing 50 mcg of estrogen. Although the relative risk is constant over the age groups, the absolute increase in cerebral thromboembolism risk by use of OCs is 10-fold higher for a 40-year-old woman (20/100,000/year) than a 20-year-old woman (2/100,000/year).