THE EFFECT ON FOLLICULAR-GROWTH AND LUTEAL FUNCTION OF MISSING THE PILL - A COMPARISON BETWEEN A MONOPHASIC AND A TRIPHASIC COMBINED ORAL-CONTRACEPTIVE

The effects on follicular growth and hormonal indices of the deliberate omission of two low-dose combined oral contraceptives, a monophasic (30-mu-g ethinylestradiol + 150-mu-g desorgestrel) and a triphasic (30-mu-g ethinylestradiol + 50-mu-g levonorgestrel for 6 days, followed by 40-mu-g ethinylestradiol + 75-mu-g levonorgestrel for 5 days and 30-mu-g ethinylestradiol + 125-mu-g levonorgestrel for 10 days) combination during the first three days of one contraceptive pill cycle was studied in two groups of 10 women each. Follicular growth was followed by ultrasound scanning and plasma levels of estradiol, and progesterone were measured every other day until day 19 of the contraceptive pill cycle. In each group, ovulation occurred in one subject and 4 women reacted with follicular activity only, while 5 women on the monophasic and 3 on the triphasic formulation exhibited complete ovarian suppression. Two subjects on the triphasic preparation showed follicular growth followed by insufficient luteal function. Thus, the risk of escape ovulation when the pill-free interval is prolonged to 10 days in women taking low-dose combined oral contraceptive pills, is low (1/10).