Ovarian activity in women taking an oral contraceptive containing 20 microg ethinyl estradiol and 150 microg desogestrel: effects of low estrogen doses during the hormone-free interval.

OBJECTIVE

We assessed the effect of low ethinyl estradiol doses given during the nominally hormone-free interval of the Mircette (brand of desogestrel/ethinyl estradiol and ethinyl estradiol) contraceptive regimen on ovarian activity.

STUDY DESIGN

In a randomized, double-blind study, healthy women received 150 microg desogestrel and 20 microg ethinyl estradiol for 21 days followed by either placebo for 7 days (Mircette/placebo; N = 24) or placebo for 2 days and 10 microg ethinyl estradiol for 5 days (Mircette/ethinyl estradiol; N = 23).

RESULTS

During cycles 2 and 3, the Mircette/placebo group had a higher incidence of persistent ovarian follicles (eight subjects versus three subjects) and on average a greater maximum follicle diameter than the Mircette/ethinyl estradiol group. One Mircette/placebo subject probably ovulated in cycle 2, and another had a luteinized unruptured follicle; no such activity was seen in the in the Mircette/ethinyl estradiol group. The study medication was well tolerated, and there were no apparent between-group differences in vaginal bleeding patterns.

CONCLUSION

The Mircette regimen, which includes low ethinyl estradiol doses during the hormone-free interval, more effectively suppresses ovarian follicular activity with a low monthly estrogen dose.