Adding human chorionic gonadotropin to frozen-thawed embryo transfer cycles pretreated with GnRH-a improves clinical pregnancy rates: a retrospective study.

This study evaluated whether intramuscular human chorionic gonadotropin (HCG) administration before endometrial transformation improves outcomes in frozen-thawed embryo transfer (FET) cycles pretreated with gonadotrophin-releasing hormone agonist (GnRH-a). We retrospectively analyzed 579 GnRH-a down-regulated hormone replacement FET cycles. Patients were divided into an HCG group (n=299 cycles, received HCG) and a control group (n=280 cycles, no HCG).The HCG group demonstrated significantly higher clinical pregnancy rates (58.5% vs. 49.3%, p<0.05) and embryo implantation rates (53.0% vs. 42.2%, p<0.05) compared to controls. Subgroup analysis showed HCG significantly increased clinical pregnancy rates in blastocyst transfer cycles (63.7% vs. 52.8%, p<0.05) but not in cleavage-stage transfers (52.5% vs. 43.3%, p>0.05). Multivariate logistic regression, adjusting for confounders, identified HCG administration as an independent factor positively associated with clinical pregnancy (OR = 1.751, 95% CI = 1.227-2.500, p=0.002).Administering intramuscular HCG before endometrial transformation in FET cycles pretreated with GnRH-a may improve  clinical pregnancy rate and embryo implantation rate.