Research question: Does intrauterine administration of HCG before embryo transfer improve live birth rate during IVF cycles?

Design: A parallel, randomized controlled trial conducted between July 2018 and February 2020. Infertile women (n = 181) scheduled for fresh or vitrified-warmed embryo transfer after IVF carried out for any indication were randomized in a 1:1 ratio to receive either HCG (500 IU in 0.1 ml of tissue culture media) or culture media (0.1 ml of tissue culture media) via intrauterine injection 4 min before embryo transfer. In both groups, an intrauterine insemination catheter was used for administering the medication. Primary outcome was live birth, with ongoing pregnancy and clinical pregnancy as secondary outcomes. Analysis was based on intention-to-treat principle.

Results: Baseline and cycle characteristics were comparable between the two groups. In the control group, one woman with a confirmed clinical pregnancy was lost to follow-up. Live birth rates were 24% (22/90) in the HCG group versus 19% (17/90) in the control group (RR 1.29, 95% CI 0.74 to 2.27). Clinical pregnancy and ongoing pregnancy rates were 34% versus 26% (RR 1.31, 95% CI 0.84 to 2.04) and 24% versus 19% (RR 1.29, 95% CI 0.74 to 2.27) in the HCG and the control groups, respectively.

Conclusion: Intrauterine injection of HCG before embryo transfer did not improve live birth rates in women undergoing IVF. As the study was designed to detect a 20% difference between groups, a smaller, clinically important difference could not be ruled out. Treatment outcomes were lower than expected in the control group.