Introduction
stenosis
STENOSIS
Due to recent developments in clinical practice and laboratory technology, embryo cryopreservation has become a central component of assisted reproductive technology (ART). Improved laboratory technology has contributed to an increased number of embryos available for Despite the emerging importance of the FET cycle, optimal endometrial preparation before it remains unclear. Although several randomized trials have examined the effects of different cycle regimens on FET, there is still no evidence for a single optimal endometrial priming protocol for FET cycles (In contrast to estrogen, progesterone appears to be a significant determinant of the WOI because the endometrial WOI is confined to the stenosis interval in the luteal phase (As for the lack of evidence regarding to the optimal duration of progesterone administration, there is still much more to be learned about endometrial preparation and synchronization to maximize endometrial function and receptivity, and select the best time for embryo transfer (