Abstract: Objective：To investigate the pregnancy outcomes of in vitro fertilization-embryo transfer （IVF-ET） related to the progesterone-to-follicle index（ＰＦＩ）, which is the ratio of serum progesterone level to the number of follicle with diameter≥14 mm on the day of hCG administration in IVF cycles. Methods：A retrospective analysis was performed on the data of 384 IVF cycles between January 2013 and August 2013. The level of progesterone and PFI were compared between pregnancy patients and non-pregnancy patients. 384 cycles were divided into three groups according to PFI, group A with PFI＜0.05, group B with PFI 0.05-0.10, and group C with PFI≥0.10. The basic information and pregnancy outcome were analyzed. Results：The level of progesterone and PFI in the pregnant group were significantly lower than those in the non-pregnant group （Ｐ＜０．０５）. The levels of estradiol in the group A and the group B were significantly higher than that in the group C （Ｐ＜０．０５）. The level of progesterone in the group A was significantly lower than those in the group B and the group C, while the level of progesterone in the group B was significantly lower than that in the group C （Ｐ＜０．０５）. The implantation rate in the group A was significantly higher than that in the group C （Ｐ＜０．０５）. Conclusions：The higher PFI on the hCG day may predict adverse implantation outcome of IVF-ET.

Key words: Progesterone, Ovarian follicle, Implantation outcome