Purpose - Intrauterine human chorionic gonadotropin (hCG) infusion at the time of embryo transfer (ET) has resulted in controversial results. We evaluated the effects of intrauterine infusion of a small volume of hCG at the time of ET in fresh and frozen-thawed cycles.

Methods -  Infertile women scheduled for ET with either fresh or frozen-thawed cycles were enrolled and randomized into two groups (n = 100 each): an hCG group, who received 500 IU of hCG in 10 µL culture medium infused into the uterine cavity using a soft catheter 4 min before ET; and a control group, who received 10 µL of culture medium alone by the same technique. The primary outcome was the implantation rate. The secondary outcomes were clinical pregnancy and live birth rate.

Results - Two hundred infertile women aged 18-43 years, undergoing fresh or frozen-thawed ET were enrolled, regardless of any previous transfer cycles. The implantation rate was significantly higher in the hCG group compared with the control group (28.8% vs. 18.2%, p = 0.030). The clinical pregnancy rates were similar in both groups (42% vs. 30%, p = 0.077). The live birth rates were also similar (29% and 23% in the hCG and control group, respectively).

Conclusions - Intrauterine infusion of a small volume of hCG at the time of ET can significantly improve the implantation rate, while the clinical pregnancy rate may only be improved in younger patients (aged < 40 years). This technique may thus be of benefit to patients undergoing clinical infertility treatment.