The use of GnRH-agonist trigger for the final maturation of oocytes in normal and low responders undergoing planned oocyte cryopreservation

STUDY QUESTION: Does GnRH-agonist trigger offer similar maturity rate (MR) in low and normal responders compared to high responders in women undergoing planned oocyte cryopreservation, for whom even a small risk of ovarian hyperstimulation syndrome (OHSS) may not be acceptable? SUMMARY ANSWER: GnRH-agonist is an appropriate choice for final maturation of oocytes in planned oocyte cryopreservation, regardless of response to stimulation or risk of ovarian hyperstimulation syndrome. WHAT IS KNOWN ALREADY: Numerous studies have demonstrated the utility of GnRH-agonist trigger for the prevention of ovarian hyperstimulation in high-responder in vitro fertilization cycles. Limited data exist supporting its use in normal or low responders, or in non-infertile women undergoing planned oocyte cryopreservation. STUDY DESIGN, SIZE, DURATION: Retrospective cohort study of 1189 subjects including all planned oocyte cryopreservation cycles performed at a large, single center, oocyte cryopreservation program from April 2016 to December 2018. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 1680 cycles were included in the study. A total of 57.1% (959/1680) utilized GnRH-agonist for trigger. Demographic and clinical data were collected from the medical record. Maturation rate was calculated for the entire cohort, and by trigger type, using the quotient of Metaphase II (MII) oocytes and retrieved oocytes. A sub-cohort of GnRH-agonist trigger cycles were categorized by peak estradiol (E2) levels and maturation rates compared between groups. Associations were made using Student's t test, ANOVA, Mann-Whitney U and Kruskal-Wallis, where appropriate. A sample size calculation for 90% power with a significance of 5% to detect non-inferiority of <0.05 from a 0.75 maturity rate between subjects with E2 > 3000 pg/mL and E2 < 3000 pg/mL demonstrated the need for at least 116 cycles per group. MAIN RESULTS AND THE ROLE OF CHANCE: Mean MR was 0.71 ± 0.19 overall, and 0.73 ± 0.18 in the sub-cohort of GnRH-agonist trigger cycles. A total of 611 cycles (63.7%) had peak E2 < 3000, and 331 (34.5%) had E2 > 3000. No significant difference in maturity rate was noted between cycles with E2 levels >3000 pg/mL and <3000 pg/mL (0.72 ± 0.19 vs. 0.74 ± 0.14, P = 0.18), confirming the non-inferiority of maturity rates with GnRH-agonist triggers in cycles with peak E2 < 3000 pg/mL. While lower mean oocytes retrieved and mean MII oocytes were associated with lower peak E2 levels, maturity rate did not significantly differ amongst E2 level groups. Cycles with E2 < 1000 pg/mL had lower MR irrespective of trigger type. LIMITATIONS, REASONS FOR CAUTION: The retrospective nature cannot entirely exclude selection biases, confounding factors or additional variables that could not be accounted for or were not collected by the electronic medical record. Given the nature of planned oocyte cryopreservation, studies of ongoing pregnancy rates and birth outcomes will naturally be delayed. Lastly, the study population was limited to women undergoing planned oocyte cryopreservation; therefore, the results may not be generalizable to women undergoing in vitro fertilization. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study specifically comparing the efficacy of GnRH-agonist in patients at lower risk for OHSS to those at high risk, as well the first study evaluating GnRH-agonist's efficacy specifically in planned oocyte cryopreservation cycles.