Objective: To elucidate the effects of initiating oral contraceptives (OC) at defined stages of ovarian follicle development.
Design: Prospective longitudinal study.
Setting: Healthy volunteers in an academic research environment.
Patient(s): Forty-five healthy women between the ages of 18 and 35 years, randomized to initiate OC when a follicle diameter of 10, 14, or 18 mm was first detected.
Intervention(s): The OC administration at defined stages of dominant follicle development.
Main outcome measure(s): Fates of all dominant follicles and serum concentrations of E(2)-17beta, LH, and P before and after initiating OC.
Result(s): No ovulations (0/16) were observed when OC use was initiated at a follicle diameter of 10 mm, 4/14 (29%) follicles ovulated when OC were initiated at 14 mm, and 14/15 (93%) ovulated when OC were initiated at 18 mm. When ovulation did not occur, follicles regressed or became anovulatory cysts. Peak LH and E(2) levels were lowest in the 10-mm group, moderate in the 14-mm group, and greatest in the 18-mm group. Peak endocrine levels in all treatment groups were lower than the historic reference group.
Conclusion(s): Follicular development, ovulation, and endocrine concentrations were not suppressed effectively when OC were initiated at late stages of dominant follicle development.