There is an ongoing debate regarding the impact of premature progesterone rise on the IVF outcome. The objective of this review is to assess evidence of poorer ongoing pregnancy rate in IVF cycles with elevated serum progesterone at the end of follicular phase in ovarian stimulation. It also explores the origin of the progesterone rise, potential modifying factors and possible methods to prevent its rise during ovarian stimulation. This review draws on information already published from monitoring progesterone concentrations at the end of follicular phase in ovarian stimulation. The databases of Medline and PubMed were searched to identify relevant publications. Good-quality evidence supports the negative impact on endometrial receptivity of elevated progesterone concentrations at the end of the follicular phase in ovarian stimulation. Future trials should document the cause and origin of premature progesterone in stimulated IVF cycles. There is an ongoing debate regarding the impact of premature progesterone rise on the IVF outcome. The objective of this review is to assess evidence of poorer ongoing pregnancy rate in IVF cycles with elevated serum progesterone at the end of follicular phase in ovarian stimulation. It also explores the origin of the progesterone rise, potential modifying factors and possible methods to prevent its rise during ovarian stimulation. This review draws on information already published from monitoring progesterone concentrations at the end of follicular phase in ovarian stimulation. The databases of Medline and PubMed were searched to identify relevant publications. Good-quality evidence supports the negative impact on endometrial receptivity of elevated progesterone concentrations at the end of follicular phase in ovarian stimulation. Future trials should document the cause and origin of premature progesterone in stimulated IVF cycles.