Effect of preovulatory insertion of Norplant implants over luteinizing hormone secretion and follicular development

To determine whether the process of ovulation could be interrupted by the insertion of Norplant implants (Leiras Pharmaceuticals, Turku, Finland) in the advanced preovulatory phase.

Prospective study.

The Department of Biomedical Research at the Family Planning Clinic of PROFAMILIA, Santo Domingo, Dominican Republic.

Healthy women of reproductive age, requesting Norplant implants contraception. Thirteen of 15 women volunteers who were admitted completed the study.

Norplant implants were inserted when the dominant follicle reached a mean diameter of 16 mm, based on serial vaginal ultrasounds (US) beginning on day 10 of the cycle. Blood samples for determination of E2, P, LH, and levonorgestrel, were taken and vaginal US performed at 0, 4, 24, 48, and 72 hours after insertion. If follicle rupture had not occurred at 72 hours after insertion, blood sampling and US were done three times per week during 2 additional weeks.

Follicle rupture occurred in 11 of 13 subjects within 72 hours after insertion, with the exception of 1 subject in whom rupture occurred between 72 and 192 hours. Two women already had an LH peak at the time of insertion. In 9 of the remaining 11 women, a shortlasting, blunted LH surge was observed at 4 hours postinsertion. In the remaining two women, who had the lowest E2 levels, ovulation was inhibited, and a persistent follicle developed without luteinization.

The insertion of Norplant implants in the advanced follicular phase will not inhibit ovulation if sufficient E2 priming has occurred. On the contrary, the exogenous progestin may rapidly foster ovulation shortly after.