Gonadotropin-releasing hormone agonist downregulation combined with hormone replacement therapy improves the reproductive outcome in frozen–thawed embryo transfer cycles for patients of advanced reproductive age with idiopathic recurrent implantation failure

BACKGROUND: To determine whether gonadotropin-releasing hormone (GnRH) agonist downregulation combined with hormone replacement therapy (HRT) can improve the reproductive outcomes in frozen–thawed embryo transfer cycles for older patients (aged 36–43 years) with idiopathic recurrent implantation failure (RIF). METHODS: This retrospective cohort study involved 549 older patients undergoing their third cleavage-stage embryo or blastocyst transfer over a 5-year period (January 2015–December 2020) at Northwest Women’s and Children’s Hospital after in vitro fertilization/intracytoplasmic sperm injection cycles. Patients with known endometriosis or adenomyosis were excluded from the study. The patients were divided into three groups according to the endometrial preparation protocol: the natural cycle (NC) group (n = 65), the HRT group (n = 194), and the GnRH agonist downregulation combined with HRT cycle (GnRH agonist–HRT) group (n = 290). The primary outcome was the live birth rate, and the secondary outcomes were the clinical pregnancy, miscarriage, and ongoing pregnancy rates. RESULTS: The live birth rate in the GnRH agonist–HRT group (36.55%) was higher than that in the HRT group (22.16%) and NC group (16.92%) (P < 0.0001). Similarly, a logistic regression model adjusting for potential confounders showed that the live birth rate was higher in the GnRH agonist–HRT group than in the HRT group (odds ratio, 0.594; 95% confidence interval, 0.381–0.926; P = 0.021) and NC group (odds ratio, 0.380; 95% confidence interval, 0.181–0.796; P = 0.010). CONCLUSIONS: The GnRH agonist–HRT protocol improves the live birth rate in frozen–thawed embryo transfer cycles for patients of advanced reproductive age with RIF. We hypothesize that the GnRH agonist–HRT protocol enhances implantation-related factors and promotes optimal endometrial receptivity, leading to an improved live birth rate. These findings are also useful for further investigating the underlying mechanism of the GnRH agonist–HRT protocol in improving the reproductive outcomes for patients of advanced reproductive age with RIF. TRIAL REGISTRATION: This research protocol was approved by the hospital institutional ethics committee (No. 2021002).