[Contraceptive effect of low-dosage ovulation inhibitors containing various progestagen agents]

The decrease of steroid dosage in oral contraceptives resulted in a decrease of serious side effects with continued effectiveness. However, a increase in subjectively disturbing bleeding abnormalities occurred at the same time. The development of triphasic preparations was designed to eliminate these abnormal bleeding episodes by stepwise changes of the estrogen and progestagen doses. Compared to the low dosage combination preparation, triphasic preparations show often a persistence of insufficiently suppressed hormone levels in single determinations but not in mean averages of determinations. This could be an explanation for the reported pregnancies. In spite of these results, the literature reports rare failures during the administration of the triphasic preparations and additional factors could determine the contraceptive effectiveness.