Differences in the luteal phases after failed or successful in vitro fertilization and embryo replacement

Luteal phases after in vitro fertilization (IVF) and embryo replacement have been studied in 241 cycles. A positive correlation was observed between the follicular estradiol (E₂) peak and the progesterone (P) level on day 3 of the luteal phase, but not correlation was found between the E₂-peak value and the luteal-phase duration or midluteal P concentration. When the trials were classified in relation to their outcome (i.e., clinical pregnancies, chemical pregnancies, or failures), the mean P level on day 3 of the luteal phase was significantly higher in clinical pregnancies than in chemical pregnancies and in failures. Mean E₂ levels on day 3 were not significantly different among the three groups. Values of the E₂/P ratio were significantly higher in chemical pregnancies than in the other groups. No significant differences were observed among the three groups on day 8. When comparing trials ending in failure to those leading to clinical pregnancy for the same patients, pregnancies were obtained in cycles in which early luteal P was higher and the early luteal E₂/P ratio was lower than in failures cycles. These data suggest that high P levels and a low E₂/P ratio in the early luteal phase might have a favorable influence on the implantation process in human IVF.