Contraceptive efficacy of a monophasic oral contraceptive containing desogestrel

Desogestrel, a new gonane progestin, has been shown to be comparable in efficacy with oral contraceptives currently in use in the United States. Results from several large efficacy studies conducted in Europe encompassing 42,640 patients in 183,212 cycles resulted in six pregnancies for a Pearl index of 0.04. This low rate, which was compared with those observed in recent U.S. clinical trials, reflects differences in study methodology. An additional indicator of an oral contraceptive's efficacy is its ability to suppress ovarian function, including follicular development and increases in plasma estradiol levels. Desogestrel has been found to be among the strongest suppressors of ovarian activity.