Effect of progesterone elevation in follicular phase of IVF-cycles on the endometrial receptivity

Abstract The premature rise of progesteroneduring the late follicular phasein stimulated IVF cycles is a frequent event, and emerging evidence shows that premature progesteronerise does negatively affect the outcome of assisted reproductive techniques. The effect of elevated peripheral progesteronelevels in the late follicular phaseseems to be on the endometriumand the window of implantation, which may lead to asynchronybetween the endometriumand the developing embryo. In stimulated cycles, endometrial maturation is advanced on the day of oocyte retrieval, and patients with a progesteronelevel above 1.5 ng/ml on the day of final oocyte maturation have different endometrial gene expression profiles. This progesteronelevel seems to represent the critical threshold, at which a negative effect on the ongoing pregnancy rate in fresh IVF cycles can be observed. Moreover, no association exists between progesteroneelevation in the fresh cycle, and the probability of pregnancy after transfer of frozen–thawed embryos, originating from that cycle. The causes of premature progesteroneelevation during ovarian stimulation are still unclear; however, recent studies point towards enhanced FSH-stimulation as a cause for progesteroneelevation.