Preovulatory follicular fluid: relationships to ovarian stimulation protocol, fertilization, and sperm penetration in vitro

Sixty follicular fluids were aspirated from 21 patients undergoing in vitro fertilization. Twelve patients (30 follicles) were stimulated with follicular phase gonadotropin-releasing hormone-agonist (GnRH-a) and gonadotropins and 9 (30 follicles) were given clomiphene citrate (CC) and gonadotropins. Significantly higher progesterone (P), P/estradiol (E2) ratios and lower E2, luteinizing hormone (LH), and human chorionic gonadotropin levels were found in the follicles of patients given GnRH-a compared with CC. Preovulatory plasma LH, P, and E2 were lower in the GnRH-a group but these comparisons were not significant. Fertilization rates were similar in the two treatment groups and no differences were found between fluids yielding fertilized or unfertilized oocytes. Sperm penetration into the zona pellucida was unrelated to follicular components. Possible physiological explanations are discussed.