Premature luteinization during gonadotropin-releasing hormone antagonist cycles and its relationship with in vitro fertilization outcome.

OBJECTIVE: To determine the prevalence and the effect of premature luteinization in GnRH antagonist IVF-ET cycles. DESIGN: Prospective observational study. SETTING: In vitro fertilization-embryo transfer (IVF-ET) program at the Instituto Valenciano de Infertilidad. PATIENT(S): Eighty-one infertile patients undergoing controlled ovarian hyperstimulation with gonadotropins and GnRH antagonist for IVF-ET. INTERVENTION(S): Gonadotropin-releasing hormone (GnRH) antagonist was administered from stimulation day 6. Serum P, E(2), and LH were determined on the day of hCG administration. MAIN OUTCOME MEASURE(S): Cycles were grouped according to serum P level on the day of hCG administration (<1.2 ng/mL or > or =1.2 ng/mL). Clinical pregnancy and implantation rates were determined. RESULT(S): The incidence of premature luteinization was 38.3%. Total recombinant FSH dose and stimulation days differed significantly between the groups. Pregnancy rate (25.8% vs. 54.0%) and implantation rate (13.8% vs. 32.0%) were significantly lower in the premature luteinization group. CONCLUSION(S): Premature luteinization during GnRH antagonist IVF-ET cycles is a frequent event that is associated with lower pregnancy and implantation rates. Progesterone elevations are not related to serum LH levels and may reflect the mature granulosa cell response to high FSH exposure.