Identifying women with a narrow window of embryo implantation using the endometrial receptivity assay

Abstract

The window of implantation (WOI) is believed to be at least several days wide. It should not make a difference in pregnancy rates if an IVF program chooses to perform frozen embryo transfers (FET) after 120 hours of progesterone or after 144 hours of progesterone exposure. The endometrial receptivity assay (ERA) has been used to improve pregnancy rates in women who have failed to achieve pregnancy after multiple embryo transfers. Since the ERA utilizes an endometrial biopsy performed after 120 hours exposure to progesterone, it is not clear if it can be applied to women in an IVF program performing FET after 144 hours of exposure to progesterone. An ERA was performed on a series of patients who had failed to achieve pregnancy after transfer of multiple good quality embryos. FET in these women had been executed after approximately 144 hours of progesterone exposure to estrogen prepared endometria. The ERA produced a recommendation for a change in the duration of progesterone exposure in 70.8% of the women tested. Changes in progesterone duration based on ERA testing led to an implantation rate of 50% and a live birth rate of 76.5%. This compares to an implantation rate of 3.4% and a live birth rate of 1.1% for embryo transfers before ERA testing.