Abstract: During controlled ovarian stimulation (COS), the concentration of serum progesterone sometimes increases on the day of human chorionic gonadotropin (hCG) administration. The occurrence rate of increased progesterone level was different, due to the different cutoff value based on some publications. The progesterone concentration is positively related to the number of mature follicles, the estradiol level and the total administration dose of follicle-stimulating hormone(FSH). The premature progesterone elevation could change endometrial gene expression, accelerate endometrial maturation, and affect endometrium from early- to mid-secretory phase, which result in the developmental asynchronism between endometrium and embryo, and affect the endometrial receptivity. The progesterone elevation on the day of hCG is negatively related to the implantation rate and the rate of live birth in IVF. Those negative effects of progesterone elevation can be avoided by the moderate COS protocol, the low dose of FSH, the earlier administration of hCG, the frozen-thawed embryo transfer, and the blastocyst embryo transfer.

Key words: Chorionic gonadotropin, Progesterone, Superovulation, Fertilization in vitro, Pregnancy rate