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

New low-dose oral contraceptives (OCs) containing 20 mcg of ethinyl estradiol are associated with reduced suppression of follicle-stimulating hormone with the resultant increased potential for ovarian follicular activity. This randomized double-blind study evaluated the effect on ovarian activity of low doses of ethinyl estradiol compared with placebo during the OC hormone-free interval. Women attending Withington Hospital in Manchester England received a Mircette brand OC containing 150 mcg of desogestrel and 20 mcg of ethinyl estradiol for 21 days followed by either placebo for 7 days (n = 24) or placebo for 2 days and 10 mcg of ethinyl estradiol for the final 5 days of the cycle (n = 23) for a total of three cycles. Ovarian suppression was assessed by ultrasonographic evaluations of ovarian follicular development and blood levels of 17 beta-estradiol and progesterone. During cycles 2 and 3 more women in the Mircette/placebo group than the Mircette/ethinyl estradiol group had persistent ovarian follicles (8 and 3 respectively) and there was a greater incidence of follicles 25-30 mm in diameter in the former group. One woman in the Mircette/placebo group probably ovulated in cycle 2; another had a luteinized unruptured follicle. Progesterone levels indicative of luteinization were observed in 2 women in the Mircette/placebo group but none in the Mircette/ethinyl estradiol group. There were no apparent differences between the two groups in vaginal bleeding patterns. These findings suggest that the Mircette regimen which includes low ethinyl estradiol doses during the hormone-free interval suppresses ovarian follicular activity effectively while lowering the total estrogen load administered.