Intramuscular injection of human chorionic gonadotropin before secretory transformation significantly improves the implantation and pregnancy outcomes in frozen embryo transfer cycles

To explore the effect of intramuscular injection of human chorionic gonadotropin (hCG) before secretory transformation on pregnancy outcomes of hormone replacement treatment frozen embryo transfer cycles (HRT-FET). Retrospective cohort study. Infertility patients younger than 43 years and performing HRT-FET cycles in center for Reproductive Medicine were recruited in this study. Patients suffering from adenomyosis were excluded. And a total of 904 HRT-FET cycles were analyzed, 404 cycles in the hCG group and 500 in the control group, respectively. Patients in the hCG group received intramuscular injection of 10,000 IU hCG before secretory transformation. The control group performed FET without hCG administration before secretory transformation. We compared the implantation rate (IR), clinical pregnancy rate (CPR), ongoing pregnancy rate (OPR) and live birth rate (LBR). The basic characteristics and clinical parameters were comparable between the two groups. The CPR (58.7 % vs. 49.6%; odds ratio (OR), 1.4; 95% confidence interval (CI), 1.1–1.8; P =0.007), OPR(50.0% vs. 41.2%; OR, 1.4; 95% CI, 1.1-1.9; P =0.008), LBR (47.5 % vs. 38.2%; OR, 1.5; 95% CI, 1.1-1.9; P =0.005) and IR (43.8% vs. 34.6%, P =0.000) were statistically significantly higher in the hCG group as compared with the control group. After adjusting confounding factors (age at index IVF/ICSI cycles, duration of subfertility, body mass index, number of embryos transferred and good-quality embryos transferred, and cycles of previous transfer), the use of hCG was still a significant factor predictive of LBR in HRT-FET cycles (adjusted OR 1.5; adjusted 95% CI 1.1-2.1; P =0.002). When the analysis was restricted in the patients with age < 39 years old and with at least one good embryo transferred in the included cycles, the pregnancy rates in the hCG group were more superior to the control group with statistically significant difference (CPR: 64.3% vs. 52.3%; adjusted OR, 1.6; adjusted 95% CI, 1.2-2.3; P =0.001. OPR 56.5 % vs. 45.4%; adjusted OR, 1.6; adjusted 95% CI, 1.2-2.2; P =0.002; LBR: 53.7% vs. 41.7%; adjusted OR, 1.7; adjusted 95% CI, 1.2-2.3; P =0.001). Intramuscular injection of 10,000 IU hCG before secretory transformation statistically significantly improved IR and pregnancy outcomes in HRT-FET cycles.