Which is the Preferred Endometrium Preparation in the Thin Endometrium Patients for Frozen-thawed Embryo Transfer: Moderate Ovarian Stimulation or Hormone Replacement Therapy Protocol? A Retrospective Cohort Study

Abstract Purpose: To compare the pregnancy outcomes of frozen-thawed embryo transfer (FET) with different endometrium preparation protocols among patients with thin endometrium, including moderate ovarian stimulation (MOS) and hormone replacement therapy (HRT). Methods:A retrospective cohort study was conducted among patients with endometrium ≦ 7mm. A total of 104 FET cycles were included and analyzed in two groups according to the endometrial preparation protocols, including 52 cycles in the MOS group and 52 cycles in the HRT group, respectively. The primary outcomes consisted of the clinical pregnancy rate and live birth rate. Results:After adjusting for confounders with multivariable logistic regression, clinical pregnancy rate in the MOS group appeared to be significantly higher than that in the HRT group (40.38% vs. 19.23%; aOR 3.02, 95% CI 1.11-8.17, P=0.030). The significant improvement of live birth rate in the MOS group was shown only before adjustment (30.76% vs. 13.46%; OR 2.73, 95% CI 1.01-7.37, P=0.047; aOR 2.51, 95% CI 0.84-7.51, P=0.100). In addition, biochemical pregnancy rate (48.08% vs. 28.85%, P=0.044) and ongoing pregnancy rate (30.76% vs. 13.46%, P=0.033) of the MOS group were higher than those in the HRT group, while no significant difference was found in ectopic pregnancy rate (P=1.000), miscarriage rate (P=1.000), gestational age at delivery (P=0.626), birth weight (P=0.278) and birth length (P=0.662). Conclusion:Compared with HRT, MOS protocol could be an alternative strategy to improve the clinical pregnancy rate of patients with thin endometrium for the FET cycle.