A Prospective Cohort Study on the Impact of Delaying Ovulation Trigger on Assisted Reproductive Technology Outcomes

Abstract

In assisted reproductive technology (ART), women undergo controlled ovarian stimulation (COS), which gives rise to a heterogeneous cohort of follicles that may contain oocytes of varying competency and maturity. The size of the follicle and oocyte competence are positively correlated. 1 Various studies from the literature have shown that bigger follicles presumably have mature oocytes, which potentially develop into good-quality embryos. [2][3][4][5][6][7][8][9][10][11] A recent study also showed that oocytes obtained from follicles measuring 19-24.5 mm in diameter during retrieval resulted in the formation of goodquality blastocysts. 12 The optimal size of the leading follicle at which ovulation trigger should be given in the gonadotropin-releasing hormone (GnRH) antagonist protocol has not been validated yet. With this background, we carried out a study to assess the role of delaying ovulation triggering, with the leading follicle beyond 20 mm, in enabling the maturation of medium-sized follicles during COS. We assessed the total number of oocytes collected, oocyte maturation rate, and the number of metaphase II oocytes as primary objectives, and the resulting total number of embryos available for freezing, fertilization rate, and the number of grade I embryos were considered as secondary objectives.