Effect of preovulatory progesterone administration on the endometrial maturation and implantation rate after in vitro fertilization and embryo transfer.

Fifty-two women, who had 62 ovum aspiration cycles, received a progesterone (P) supplementation of 100 mg/day that was initiated 10 hours before human chorionic gonadotropin (hCG) administration and was continued over the following 6 days. Forty-eight women who had 74 ovum pick-ups, but did not get P, served as controls. Forty-four (84.6%) women of the treatment group, and 40 (83.3%) of the controls had ovum fertilization and embryo replacement. The fertilization and cleavage rates and the mean number of replaced embryos per embryo transfer (ET) cycle did not differ between the groups. Endometrial biopsies, from treatment group women with no fertilized eggs, which were taken 48 hours after ovum pick-up, mostly revealed an "advanced endometrial dating," in relation to the "day of hCG." Pregnancy rate per ET cycle for the treatment group was significantly higher than that of the controls; 41.2% versus 23.3%, respectively. It is concluded that the higher pregnancy rate resulted from an improvement in uterine receptivity.