Effect of clomiphene citrate on in vitro ovulated ova.

The effect of clomiphene citrate (CC) on developmental capacity of ovulated ova was studied with isolated in vitro perfused rabbit ovaries. Fifty-two ovulated ova were recovered from ovaries perfused with human chorionic gonadotropin (hCG) in a medium containing CC and 45 ova from ovaries perfused with hCG in a CC-free medium. Ova were cultured and inseminated with capacitated sperm and observed serially for evidence of fertilization and stage of development. CC did not affect the fertilization of ovulated ova. However, the percentage of ova which had reached the morula stage by 60 hours was significantly reduced in the CC-treated (15.4%) group, compared with the control group of ovaries (48.9%). A significant percentage of inseminated ova from CC-treated ovaries (65.4%) showed evidence of degeneration, as compared with control ovaries (37.8%). Thus, a partial loss of developmental capacity may explain the discrepancy observed between the rate of successful ovulation induction and the establishment of pregnancy associated with CC administration in humans.