What are the best predictors for successful GnRH antagonist protocol in in vitro fertilization (IVF) treatment?

Objective: To determine factors that affect the success rate of GnRH antagonist protocol in in vitro fertilization (IVF) treatment.Design: Retrospective cohort study.Patients: Patients who underwent IVF cycle with their first GnRH antagonist protocol.Intervention: Antagonist protocol during IVF treatment. The main outcome measurements were; Number of retrieved oocytes, embryo quality and pregnancy rate.Results: Gravidity was negatively correlated with number of eggs (p = 0.017), while total follicle number ≥15 (p = 0.044) and E₂ on day of human chorionic gonadotropin (HCG) (p = 0.000) had a positive correlation with number of eggs. Maximum follicle size at HCG administration showed a trend toward an inverse correlation (p = 0.053). Addition of LH to drug stimulation was negatively correlated with number of eggs in comparison to rFSH only (p = 0.013 and 0.0000, respectively). Age and number of frozen eggs were negatively correlated with successful pregnancy (p = 0.025 and 0.004, respectively), while embryo quality, gravidity and number of embryos were positive (p = 0.011 and 0.014, respectively).Conclusion: Controlled parameters like timing of antagonist start, duration of antagonist and the optimal leading follicle diameter for HCG triggering had no effect on treatment outcomes.