['To determine if embryos can modulate steroid hormone production by luteinized granulosa cells.', 'Granulosa cells obtained from follicular aspirates were cultured alone or in the presence of a two-pronuclear zygote. The production of E2 and P by these cultures was evaluated by RIA.', 'In Vitro Fertilization Unit in an academic research environment.', 'Sixteen women undergoing IVF.', 'Standard IVF-ET treatment cycle using leuprolide acetate for pituitary desensitization before hMG or urofollitropin for ovarian stimulation.', 'Estradiol and P concentration in culture media of luteinized granulosa cells alone or granulosa cells cocultured with a two-pronuclear embryo.', 'Both E2 and P production by luteinized granulosa cells was reduced when cultured in the presence of an embryo.'] Does autologous granulosa cell coculture demonstrate zygote suppression of granulosa cell steroidogenesis?