The effect of the antiprogestin mifepristone (RU 486) on maturation and in-vitro fertilization of human oocytes.

The effect of RU 486 (mifepristone), a potent antiprogestin, on the in-vitro fertilization of human oocytes was investigated. In 40 normal volunteer women requesting laparoscopic sterilization, follicle aspiration for oocyte recovery was attempted 34 h after the injection of 5000 i.u. human chorionic gonadotrophin (hCG). Twenty women were allocated to receive 100 mg RU 486 orally 1 h before the hCG injection, the remaining 20 women acted as controls. There was no significant difference in the cleavage rate of the oocytes after fertilization in vitro between the two groups (56% and 66% respectively). Also, the morphological characteristics of the cleaving oocytes and the concentrations of oestradiol, progesterone and androstenedione in the follicular fluid of the leading follicle did not differ significantly between the two groups. Since RU 486 was detected in substantial amounts in the follicular fluid specimens, these results suggest that progesterone is not critical for the final stages of human oocyte maturation.