Intrauterine infusion of human chorionic gonadotropin before embryo transfer in IVF/ET cycle: The critical review.

Intrauterine infusion of human chorionic gonadotropin (IUI-hCG) has been proposed to improve the outcome of in vitro fertilization-embryo transfer (IVF-ET), since it plays a critical role in synchronizing endometrial and fetal development. As the early mediator from embryo, hCG promotes the decidualization, angiogenesis, maternal immune tolerance, and trophoblast invasion, favoring successful implantation of embryo. Although multiple clinical trials have been conducted to verify the efficacy of IUI-hCG on IVF-ET outcome in recent years, the findings remained controversial. The difference in study design and population might be the cause to the different consequences after administration of hCG. More importantly, the endometrial receptivity, which might affect the efficacy of IUI-hCG, has not been assessed in women receiving this intervention. Selecting the right population suitable for IUI-hCG based on known etiology would be crucial in enhancing its efficacy and minimize any possible complications. Investigation of optimal indications for IUI-hCG should be highlighted in the future.