Effect of 21-day and 24-day oral contraceptive regimens containing gestodene (60 mu g) and ethinyl estradiol (15 mu g) on ovarian activity

Objective: To compare ovulation inhibition and ovarian activity with 21-day and 24-day regimens of a low-dose combined oral contraceptive (COC) contai ning 60 mu g of gestodene and 15 mu g of ethinyl estradiol. Design: Interventional observational study. Setting: Reproductive medicine unit. Patient(s): Fifty-eight healthy volunteers aged 18-35 years. Intervention(s): Ovarian activity was monitored every other day with the us e of ultrasound to measure the diameters of follicle-like structures and bl ood samples to measure serum concentrations of 17 beta-E-2 and progesterone . Subjects were observed for five cycles: pretreatment and posttreatment co ntrol cycles and three cycles in which the COC was administered for either 21 or 24 days of each cycle. Main Outcome Measure(s): Occurrence of ovulation and evidence of ovarian ac tivity. Result(s): The study was completed by 27 (90%) of the 30 subjects who recei ved the 24-day regimen and by 24 (79%) of the 28 subjects who received the al-day regimen. Ovulation was inhibited in all cycles in the 24-day group a nd in 74 of 75 cycles in the 21-day group. Luteinized unruptured follicles were seen in no cycles with the 24-day regimen and in 6 (8%) of 75 cycles w ith the 21-day regimen. Mean ovarian follicular development and serum 17 be ta-E-2 and progesterone levels were lower in the 24-day group. Conclusion(s): The 24-day regimen is an innovative strategy for maintaining effective ovulation inhibition at ultra-low doses of contraceptive steroid s. (Fertil Steril(R) 1999;72:115-20 (C) 1999 by American Society for Reprod uctive Medicine.)