IMPACT OF REVISED START CRITERIA FOR GONADOTROPIN-RELEASING HORMONE ANTAGONIST ON IN VITRO FERTILIZATION OUTCOMES.

The objective of this study was to determine the impact of implementing a revised gonadotropin-releasing hormone antagonist (GnRH-ant) protocol on in vitro fertilization (IVF) outcomes. This retrospective cohort study included all women who underwent IVF with a GnRH-ant protocol and fresh transfer at our academic IVF center from January 2017 to March 2021. Women were divided into two groups based on whether their cycle occurred before or after the revised GnRH-ant protocol was implemented. Women cycling before July 2020 were in the “pre-intervention” group and had GnRH-ant routinely started on treatment day (TD) 4 and/or when E2 levels reached 75 pg/mL. Women cycling during or after July 2020 were in the “post-intervention” group. For these patients, GnRH-ant was started no sooner than TD5 and only when one of the following criteria was met: 1) Lead follicle ≥ 14 mm and/or 2) E2 ≥ 500 pg/ml. Demographic and clinical data were extracted from the medical record. Groups were compared using t-tests and tests for differences in proportion. A post-hoc power analysis with α=0.05 and β=0.8 revealed the study was powered to detect a difference in mean # oocytes of 6 between groups. A total of 162 women were included in the “pre-intervention” group and 34 women in the “post-intervention” group. There were no significant differences in demographic or clinical characteristics between groups. Women in the post-intervention group had significantly greater # oocytes retrieved, peak E2 level, and # mature oocytes (M2s) (table). Biochemical, clinical, and ongoing pregnancy rates (PR) were not significantly different, although this study was not powered to detect a difference in these parameters. Delaying GnRH-ant start until TD5 or later, and when either the lead follicle is at least 14 mm or the E2 level is at least 500 pg/ml, results in more M2s compared with routinely starting GnRH-ant on TD4. Larger, adequately powered studies for pregnancy and live birth rates are necessary to determine if this translates into improved outcomes.