[Unintended effects of oral contraceptives. I.Estrogen-related effects]

Oral contraceptives are almost optimally effective but not yet perfectly safe. They can cause favourable or adverse unintended effects which cannot always be attributed to either the estrogen or the progestagen; however, in many instances a fair differentiation is possible. Type, intensity and frequency of side effects depend on dosage, duration of administration and on the structure of the substance. Some favourable side effects of estrogens are used for therapeutic purposes. Adverse side effects of estrogens are either subjectively disturbing only, or medically important, but few are life threatening. Dose dependence has been established, a structure relationship is unlikely.