Abstract
To determine the effectiveness of quick starting combined oral contraception (COC) contain 2.5 mg nomegestrol acetate and 1.5 mg estradiol (NOMAC/E2) comparing with 0.075 mg gestodene and 0.02 mg ethinyl estradiol (GS/EE) on ovarian ovulation inhibition rate, we conducted a non-inferiority randomized controlled trial involving 69 healthy female volunteers aged 18-40 years who had normal menstrual history and were randomized at a 2:1 ratio to take one pack of COC containing either NOMAC/E2 (study group) or GS/EE (control group) starting on menstrual cycle Day7-9. The ovarian activity was assessed by using Hoogland and Skouby grading. Forty-six and 23 participants were randomized to NOMAC/E2 and GS/EE groups, respectively. Baseline characteristics were similar between groups. No significant difference was observed between the study and control groups for ovulation inhibition rate (93.4% vs. 95.6%, risk difference: -2.2%, 95% CI: -13.1, 8.8), ovarian quiescence rate (91.2% vs. 91.2%, P = 1.000), persistent cyst rate (2.2% vs. 4.4%, P = 1.000), and ovulation rate (6.6% vs. 4.4%, P = 1.000). Quick starting COC during day7-9 of menstrual cycle can inhibit ovulation for more than 90%. The quick starting NOMAC/E2 is non-inferior to GS/EE for preventing ovulation and suppressing follicular growth.