Hormone-induced delayed ovulation affects early embryonic development.

OBJECTIVE: To analyze the effects of delayed ovulation on embryonic development in mice, because intrafollicular oocyte development may be delayed during assisted reproductive technology (ART) treatment in humans.
DESIGN: Experimental mouse study.
SETTING: University hospital. ANIMAL(S): Female C57Bl/6 mice. INTERVENTION(S): Cetrorelix is used as a GnRH-antagonist in ART treatments. To assess the effect of delayed ovulation on embryonic development, cetrorelix was applied concomitantly with follicle stimulation by pregnant mare serum gonadotropin. Ovulation was induced by hCG. Controls were stimulated with pregnant mare serum gonadotropin without delaying ovulation. Suppression of ovulation was assessed from the number of tertiary follicles, ruptured follicles, and corpora lutea in mouse ovaries after cetrorelix treatment. Number and weight of embryos and placentas, as well as number of resorption sites and dead embryos, was determined on day 17.5 of pregnancy. MAIN OUTCOME MEASURE(S): Inhibition of ovulation, embryonic development. RESULT(S): Cetrorelix inhibited ovulation in mice, as shown by an increase in number of tertiary follicles concomitant with a significant inhibition of follicle rupture and corpora lutea formation. Delayed ovulation caused by Cetrorelix treatment led to a significant increase in resorption sites and a significant decrease in embryonic weight of offspring. CONCLUSION(S): Preovulatory oocyte overripeness might have an effect on fertility and embryonic development during ART treatment.