Endometrial Preparation for Frozen–Thawed Embryo Transfer With or Without Pretreatment With Gonadotropin-Releasing Hormone Agonist in Regular Menstrual Cycles: Results of a Retrospective Cohort Study

Abstract ObjectsTo compare the treatment outcomes of FET in hormonal replacement treatment (HRT) protocol with and without long-acting gonadotropin-releasing hormone agonist (GnRHa) pretreatment in patients with regular menstrual cycles. MethodsA total of 5049 patients from three centers were recruited in this retrospective study. The study population was divided into two groups. In HRT with GnRHa group, endometrial preparation with supplement estrogen 6mg daily initiated following down-regulation of long-acting GnRH agonist. In HRT group, the same dose of estrogen administration only for two weeks. Live birth rates were the primary outcomes measured in both groups. ResultsThere were no differences in implantation rate, β-HCG positive rate, clinical pregnancy rate, and early miscarriage rate between the two groups. The ongoing pregnancy rate and the live birth rate were higher in HRT group compared to the agonist group (47.3% vs 42.7% and 44.7% vs 39.8%, respectively). However, the co-treatment with GnRH agonist in HRT protocol was not associated with clinical pregnancy rate (OR 0.94; 95% CI 0.78 to 1.12) and live birth rate (OR 0.82; 95% CI 0.71 to 1.02) after logistic regression analysis. In the first FET cycle, patients in HRT group achieved higher clinical pregnancy rate and live birth rate. In addition, there was no differences in clinical pregnancy rate and live birth rate between the two groups in standard patients.ConclusionsThe HRT protocol for FET seems to be as effective as the HRT protocol involving preliminary pituitary suppression with GnRH agonist in regular menstrual cycles.