Ovarian follicular development is initiated during the hormone-free interval of oral contraceptive use

We evaluated ovarian follicular development in women during compliant use of oral contraceptives (OC). Thirty-six healthy women received: [35 mug ethinyl estradiol (21)/180 mug norgestimate (7), 215 mug norgestimate (7), 250 mug norgestimate (7)]; [30 mug ethinyl estradiol (21)/ 150 mug desogestrel (21)]; or [20 mug ethinyl estradiol (21)/100 mug levonorgestrel (21)] for 3 consecutive 28-day cycles. Transvaginal ultrasonography was performed every third day to monitor follicular development. If a follicle reached greater than or equal to 14 mm, ultrasonography was performed daily and blood drawn every other day to determine estradiol-17beta concentrations. Seventeen of 36 women (47%) grew follicles greater than or equal to 10 mm. Nine of the 17 women (53%) grew follicles greater than or equal to 14 mm, in association with increased serum concentrations of estradiol-17beta. Thirty-seven of 43 follicles greater than or equal to 10 mm (86%) emerged during the hormone-free interval (HFI). No ovulations were observed. Our results supported the hypothesis that follicular development to an ostensibly ovulatory diameter occurs during compliant OC use, in association with loss of endocrine suppression during the HFI. (C) 2004 Elsevier Inc. All rights reserved.