Endometrial Shedding Effect on Conception and Live Birth in Women With Polycystic Ovary Syndrome

OBJECTIVE: To estimate whether progestin-induced endometrial shedding, before ovulation induction with clomiphene citrate, metformin, or a combination of both, affects ovulation, conception, and live birth rates in women with polycystic ovary syndrome (PCOS). METHODS: A secondary analysis of the data from 626 women with PCOS from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Cooperative Reproductive Medicine Network trial was performed. Women had been randomized to up to six cycles of clomiphene citrate alone, metformin alone, or clomiphene citrate plus metformin. Women were assessed for occurrence of ovulation, conception, and live birth in relation to prior bleeding episodes (after either ovulation or exogenous progestin-induced withdrawal bleed). RESULTS: Although ovulation rates were higher in cycles preceded by spontaneous endometrial shedding than after anovulatory cycles (with or without prior progestin withdrawal), both conception and live birth rates were significantly higher after anovulatory cycles without progestin-induced withdrawal bleeding (live births per cycle: spontaneous menses 2.2%; anovulatory with progestin withdrawal 1.6%; anovulatory without progestin withdrawal 5.3%; P<.001). The difference was more marked when rate was calculated per ovulation (live births per ovulation: spontaneous menses 3.0%; anovulatory with progestin withdrawal 5.4%; anovulatory without progestin withdrawal 19.7%; P<.001). CONCLUSION: Conception and live birth rates are lower in women with PCOS after a spontaneous menses or progestin-induced withdrawal bleeding as compared with anovulatory cycles without progestin withdrawal. The common clinical practice of inducing endometrial shedding with progestin before ovarian stimulation may have an adverse effect on rates of conception and live birth in anovulatory women with PCOS.