Ovulatory effects of three oral contraceptive regimens: a randomized, open-label, descriptive trial

This study describes ovarian activity suppression of a 21/7-active low-dose combined oral contraceptive (COC) regimen that included only ethinyl estradiol (EE) during the traditional hormone-free interval (HFI) and two commercially available 28-day regimens, a 24/4 and a 21/7 regimen.

The randomized, open-label, parallel-group descriptive study was conducted at two US sites. Healthy, reproductive-aged women (n=146) were randomized to one of three groups for three consecutive 28-day cycles, as follows: treatment 1 (n=39 completed): 21/7-active COC [21 days of 150 mcg desogestrel (DSG)/20 mcg EE, followed by 7 days of 10 mcg EE (DSG/EE+7 days EE)], treatment 2 (n=39 completed): 24 days of 3mg drospirenone (DRSP)/20 mcg EE, followed by 4 placebo (PBO)-pill days (DRSP/EE+4 days PBO) and treatment 3 (n=42 completed): 21 days of 100 mcg levonorgestrel (LNG)/20 mcg EE, followed by 7 PBO-pill days (LNG/EE+7 days PBO). The primary outcome was ovarian activity suppression assessed by transvaginal ultrasound and serum hormone concentrations and classified using the Hoogland and Skouby (H/S) method.

Ovarian activity rate (H/S grade 4 or 5) was low for all three treatments: 0% [95% confidence interval (CI) 0-2.8] for DSG/EE+7 days EE, 1% (95% CI 0.2-5.2) for DRSP/EE+4days PBO and 1% (95% CI 0-3.9) for LNG/EE+7 days PBO. All three treatments showed similar suppression of serum progesterone, 17β-estradiol, follicle-stimulating hormone and luteinizing hormone levels.

The 21/7-active low-dose COC regimen (DSG/EE+7 days EE) showed ovarian activity suppression that was similar to the 24/4 (DRSP/EE+4 days PBO) and 21/7 (LNG/EE+7days PBO) regimens.

The 21/7-active low-dose COC regimen (DSG/EE+7 days EE) that included only EE during the traditional HFI showed suppression of ovarian follicular activity that was similar to the 24/4 (DRSP/EE+4days PBO) and the 21/7 (LNG/EE+7 days PBO) comparator regimens.