Intrauterine infusion of human chorionic gonadotropin improves the endometrial FoxP3+ Tregs level and pregnancy outcomes in patients with lower endometrial FoxP3+ Tregs

Intrauterine infusion of human chorionic gonadotropin (hCG) is suggested to have the capacity to recruit regulatory T cells (Tregs) in the endometrium. However, the pregnancy outcome for infertile women with a lower level of Tregs after hCG intrauterine infusion remains unknown. By examining the expression of FoxP3+ Tregs in the endometrium, this study aimed to evaluate the effectiveness of hCG intrauterine infusion in infertile women with lower endometrial Tregs in improving the Tregs level and the pregnancy outcome. This cohort study included 150 women aged 38 and younger with a lower FoxP3+ Tregs level in the mid-luteal phase. Patients were divided into the control group (n = 73), and hCG group (n = 77). Patients in the hCG group received three times of hCG intrauterine infusion during the follicular phase in the next biopsy and the embryo transfer cycles. The results showed that the endometrial FoxP3+ Tregs level increased significantly after hCG intrauterine infusion (P < 0.001). The effective rate in rescuing the endometrial Tregs level was 77.92% (60/77). The clinical pregnancy rate was increased significantly in the hCG group than the control group (54.8% vs. 74.0%, P = 0.014). The logistic regression result showed that hCG intrauterine infusion [adjusted odds ratio (aOR) (95% confidence interval (CI)) = 2.347 (1.119, 4.923), P = 0.024] and blastocyst transfer [aOR (CI) = 2.630 (1.090, 6.346)] are two independent factors contributing to the improved pregnancy outcome. These data highlighted the immune regulatory role of hCG intrauterine infusion and might facilitate the personal immunotherapy progress for unexplained infertility in patients with a lower endometrial Tregs level.