Oral contraceptive estrogen content and adverse effects.

The 1985 Health and Welfare Canada Report on Oral Contraceptives recommended oral contraceptives (OCs) containing 30-35 mcg of estrogen rather than 50 mcg as the preferred dosage for contraception. Many family physicians may regard these guidelines as mandatory when prescribing OCs, because of a presumption that pills of 50-mcg estrogen content carry a higher risk of disease. In this article, the epidemiologic evidence pertaining to a dose-response relationship between the estrogen dose of oral contraceptives and disease is critically reviewed. The review indicates that there is no incontrovertible evidence to support such a relationship. Implications of the recommendations in the Report for physicians and patients are discussed.