Effect of interval between ovulation trigger and oocyte aspiration in GnRH antagonist cycles

Oocyte aspiration was usually done 35-36 hours after triggering. Some studies evaluated the effects of interval between triggering for final oocyte maturation and oocyte aspiration in GnRH agonist long protocol. Longer interval was related with oocyte maturation rate in these studies. However, there are few studies about the effects of interval between triggering and oocyte aspiration in GnRH antagonist cycles. The purpose of this study is to evaluate the effect of interval between ovulation trigger and oocyte aspiration in GnRH antagonist cycles Prospective observational study This prospective observational study included 2079 patients undergoing IVF cycles using GnRH antagonist protocol between November 2014 and March 2017. On the day of triggering, final oocyte maturation was triggered by intramuscular hCG 10000 IU at 9 PM. And oocyte aspiration was done after 36 to 39 hours later. We divided the patients into three groups by interval between triggering and oocyte aspiration. Group A: 36 hours ≤ interval ≤ 37 hours Group B: 37 hours < interval ≤ 38 hours Group C: 38 hours < interval ≤ 39 hours In each group, age (36.9±4.1 vs. 36.8±4.1 vs. 36.9±4.0) and the number of oocytes (8.2 vs. 8.6 vs. 8.5) did not show significant differences. There were no significant differences among three groups in the percentage of mature oocytes [63.4% vs. 62.4% vs. 63.5%, P=NS] and fertilization rates [72.8% vs. 73.8% vs. 71.7%, P=NS]. Pregnancy rates were similar among three groups [46.1%(487/1056) vs. 48.1%(330/686) vs. 47.5%(159/335), P=NS]. In this study, interval between triggering for final oocyte maturation and oocyte aspiration does not affect the IVF outcomes. It suggests clinician can fix triggering injection time like 9 PM. It could give some convenience to patients and hospital staff without compromising IVF outcomes.