Follicular size at the time of human chorionic gonadotropin administration predicts ovulation outcome in human menopausal gonadotropin-stimulated cycles

Objective: The objectives of this study were: (1) to correlate follicle size by transvaginal sonography with ovulation outcome in cycles of controlled ovarian hyperstimulation with human menopausal gonadotropins; (2) to determine if follicular size on the day of human chorionic gonadotropin (hCG) administration predicts the incidence of ovulation; and, if so, (3) to derive a mathematical model that predicts the number of expected ovulations in any given cycle of controlled ovarian hyperstimulation. Design: A retrospective analysis. Participants: Forty-nine consecutive patients undergoing 122 cycles of controlled ovarian hyperstimulation were studied in a tertiary care setting. Main Outcome Measures: Follicular size and evidence of ovulation were determined sonographically. The main outcome measure was the rate of ovulation per follicle size. Results: The percentages of follicles measuring ≤14 mm, 15 to 16 mm, 17 to 18 mm, 19 to 20 mm, and >20 mm on the day of hCG administration that subsequently ovulated were 0.5%, 37.4%, 72.5%, 81.2%, and 95.5%, respectively. Conclusions: (1) Follicular size on the day of hCG administration correlates with the incidence of ovulation. (2) The expected number of ovulations in any given controlled ovarian hyperstimulation cycle can be predicted with 95% confidence using the accompanying equation.