OBJECTIVE: to study the effect of a single contraceptive implant of nomegestrol acetate (Uniplant) on the ovarian function, cervical mucus production and sperm penetration, when inserted in women in the preovulatory phase. METHODS: twenty women with regular menstrual cycles were included in an open comparative study. All participants were investigated during one menstrual cycle before (control) and one menstrual cycle after implant insertion. Measurements of estradiol, LH, and progesterone, as well as transvaginal sonography, cervical mucus examination and sperm penetration test, were carried out. Statistical analysis was performed with the paired t-test and the non-parametric test of Wilcoxon. RESULTS: all control cycles were ovulatory and presented normal parameters. Preovulatory estradiol and LH peak decreased significantly from 603.2 ± 78.0 pmo/l and 22.5 ± 6.5 IU/l at pre-insertion to 380.7 ± 51.9 pmol/l and 4.9 ± 1.3 IU/l 48 hours after implant insertion (p < 0.05 and p < 0.01, respectively). Progesterone levels did not vary significantly (control cycle = 49.8 ± 3.3 nmol/l and treated cycle = 43.2 ± 5.2 nmol/l). Cervical mucus and sperm penetration tests were profoundly affected in 10.5% of the users 20 h after implant insertion, in 68.5% after 24 h and in 100% after 48 h. Follicular rupture occurred in the majority of the cycles 48 h after implant insertion. CONCLUSIONS: the use of a single implant of nomegestrol acetate affected estradiol and LH preovulatory peaks and disrupted the process of cervical mucus production and sperm penetration, but it was unable to prevent ovulation when inserted at the preovulatory phase, which reinforces the need to insert the implant during the first five days of the menstrual cycle.
Contraceptive implant; Nomegestrol acetate; Uniplant; Cervical mucus; Sperm penetration
