Abstract: Objective: To explore the relationship between the level of serum P/E2 on the day 6 after embryo transfer of cotrolled ovarian hyperstimulation and the clinical outcomes of IVF/ICSI-ET. Methods：A total of 544 cycles of IVF-ET were divided into two groups by the level of P/E2 on the day 6 after ET: group A (P/E2＜114.5) and group B(P/E2≥114.5). The clinical data, implantation rate and clinical pregnancy rate were compared between two groups. Results：There were not significant differences between two groups in the endometrial thickness, total dose of gonadotropin, duration of gonadotropin and number of ET (P＞0.05). However, the implantation rate and clinical pregnancy rate in the group A were significantly higher than those in the group B (P＜0.05). Conclusions：The clinical outcomes will be better if the level of serum P/E2 on the day 6 after ET was lower than 114.5, suggesting that the level of serum P/E2 on the day 6 is a useful parameter predicting clinical outcomes of IVF.

Key words: Superovulation, Embryo transfer, Progestins, Estradiol, Pregnancy outcome