Abstract: There is a debate regarding the impact of the raised level of progesterone on the day of chorionic gonadotrophin （hCG） administration during late follicular phase on the outcomes of in vitro fertilization （IVF）. Based on hypothesis that the raised level of progesterone on the day of hCG injection affect IVF outcome, it was found that progesterone was produced by follicular granulosa cells, and that a variety of factors increased the progesterone production during ovarian stimulation. The effects of the raised level of progesterone on IVF outcomes were reviewed, including hormone, oocyte quality and endometrial receptivity. We can conclude that the raised progesterone could reduce the pregnant rate by the lowered endometrial receptivity. This review will be helpful for doctors to optimize their protocols of ovarian stimulation and/or embryonic transplantation, so as to improve IVF outcomes and to explore new protocol of ovarian mini-stimulation/natural cycle.

Key words: Fertilization in vitro, Embryo transfer, Down-regulation, Ovulation induction, Progesterone