Effectiveness of GnRH Agonist Short Protocol Versus GnRH Antagonist Protocol in POSEIDON Groups 3 and 4: a Retrospective Cohort Study.

The aim of this study is to compare the ART (assisted reproductive technology) outcomes and cancellation rates between GnRH antagonist protocol and GnRH agonist short protocol in POSEIDON (Patient-Oriented Strategy Encompassing IndividualizeD Oocyte Number) groups 3 and 4. It is a retrospective cohort study conducted in the Department of Reproductive Medicine and Surgery of a tertiary-level hospital. Women who underwent ART treatment with either GnRH antagonist or GnRH agonist short protocol with fresh embryo transfer, between January 2012 and December 2019 belonging to POSEIDON 3 and 4 groups, were included. Among the 295 women who belonged to the POSEIDON groups 3 or 4, 138 women received GnRH antagonist and 157 women received GnRH agonist short protocol. The median total dose of gonadotropin in the GnRH antagonist protocol was not significantly different from GnRH agonist short protocol [3000, IQR (2481-3675) vs. 3175, IQR (2643-3993), p = 0.370]. There was a significant difference in the duration of stimulation between the GnRH antagonist and GnRH agonist short protocol [10, IQR (9-12) vs. 10, IQR (8-11), p = 0.002]. The median number of mature oocytes retrieved was significantly different in the cohort of women receiving GnRH antagonist protocol compared to GnRH agonist short protocol [3, IQR (2-5) vs. 3, IQR (2-4), p = 0.029]. There was no significant difference in the clinical pregnancy rate (24% vs. 20%, p = 0.503) and cycle cancellation rate (29.7% vs. 36.3%, p = 0.290) between the GnRH antagonist and agonist short protocols respectively. Live birth rate was not significantly different between the GnRH antagonist protocol (16.7%) and GnRH agonist short protocol (14.0%) [OR 1.23, 95% CI (0.56-2.68), p = 0.604]. After adjusting for the significant confounding factors, the live birth rate was not significantly associated with the antagonist protocol compared with the short protocol [aOR 1.08, 95% CI (0.44-2.63), p = 0.870]. Though GnRH antagonist protocol results in higher mature oocyte yield when compared with GnRH agonist short protocol, it does not translate into an increase in live birth in POSEIDON groups 3 and 4.