Comparison of pregnancy outcome after fresh embryo transfer between GnRH antagonist and GnRH agonist regimens in patients with thin endometrium

OBJECTIVE: To compare the pregnancy outcome after fresh embryo transfer between GnRH antagonist and GnRH agonist regimens in patients with thin endometrium. METHODS: This retrospective study included all fresh embryo transfers following GnRH agonist or GnRH antagonist protocols in patients with thin endometrium from 2016 to 2021. The thin endometrium was defined as an endometrial thickness of 7.5 mm or less on the triggering day. Multivariant regression analysis was applied to assess the association of GnRH agonist or GnRH antagonist regimen with live birth following fresh embryo transfer in patients with thin endometrium. RESULTS: A total of 69 and 192 cases were, respectively, included in the GnRH antagonist or GnRH agonist group. The stimulation duration was significantly longer by the GnRH agonist protocol than the GnRH antagonist protocol (11.2 ± 2.1 vs. 9.1 ± 1.9 days, P = 0.002). The rates of clinical pregnancy or live birth were significantly lower in the GnRH antagonist group compared to the GnRH agonist group (26.1 vs. 47.9%, P = 0.027; 17.4 vs. 40.1%, P = 0.01, respectively). Multivariable regression analysis demonstrated that GnRH agonist regimen was related to higher live birth rate compared with GnRH agonist protocol [adjusted OR: 2.6, 95% confidence intervals (CI): 1.3–5.3]. No significant difference in miscarriage rate and the neonatal outcome was present between the two protocols. CONCLUSION: Our findings suggest that GnRH agonist protocol results in a higher rate of live birth after fresh embryo transfer than GnRH antagonist protocol in patients with thin endometrium.