Relationships between follicular fluid steroid hormone concentrations, oocyte maturity, in vitro fertilization and embryonic development in the rhesus monkey

Oocytes and matched samples of follicular fluid (FF) were obtained from 70 follicles of five rhesus monkeys stimulated with either pregnant mare serum gonadotropin or human menopausal gonadotropin. Follicular aspiration was performed 30–32 h after human chorionic gonadotropin administration. The concentrations of estradiol (E₂), progesterone (P), testosterone (T), and dihydrotestosterone (DHT) in FF were measured. Twenty‐six percent of oocytes were classified as mature (M), 41% matured in vitro (Miv), 13% were dysmature, and 20% atretic. M oocytes were associated with significantly higher levels of P and a higher P:E₂ ratio. There were no differences in hormone levels associated with fertilized and nonfertilized oocytes. Thirty‐five embryos developed to the six‐ to eight‐cell stage in vitro, of which 13 exhibited optimal cleavage rates. Significantly lower levels of E₂ and higher P:E₂ ratios were associated with the more rapidly cleaving embryos. Proportionally more embryos showing optimal cleavage rates developed from M compared to Miv oocytes, and only embryos derived from M oocytes developed to blastocysts in culture. Optimal cleavage rates to the six‐ to eight‐cell stage in vitro, rather than fertilization rates, are a better indicator of (subsequent) developmental capacity, and, in this study, embryonic development was closely associated with the maturity of the oocyte at recovery.