Abstract: Objective To compare the effect on embryo quality from gonadotropin releasing hormone(GnRH) antagonist protocol and from GnRH agonist long protocol, so as to find which protocol works better on embryo quality. Methods A retrospective analysis was performed with a total of 1 095 long protocol cycles and 1 511 antagonist protocol cycles from January 2016 to December 2019. The corresponding fertilization, embryo quality, pregnancy outcomes of the two groups, agonist vs antagonist, were calculated and analyzed. Results Antagonist group displayed significantly higher available embryo rate (29.94% vs 31.59%), good-quality two-pronuclear(2PN) embryo rate (44.67% vs 46.86%), available blastocyst/OPU(ovum pick-up)(1±2 vs 1±2) and available blastocyst rate (25.62% vs 29.66%) than the long protocol group. Conclusions Antagonist protocol may bring about more available embryos than agonist protocol. Together with a similar pregnancy outcome with agonist protocol and its efficacy in reducing ovarian hyperstimulation syndrome(OHSS) risk, antagonist protocol is the first choice for clinical contralled ovarian stimulation(COS) protocol.

Key words: gonadotropin releasing hormone, agonist long protocol, antagonist protocol, embryo quality, pregnancy outcome