Embryo quality and uterine receptivity in in-vitro fertilization cycles with or without agonists of gonadotrophin-releasing hormone

The proportion of abnormal oocytes or embryos per recovered oocyte in in-vitro fertilization (IVF) cycles had no influence on the occurrence of pregnancy following the transfer of normal embryo(s) derived from oocytes capable of fertilization. There were more implantations per transferred embryo in stimulated IVF cycles using long-acting buserelin (30.0%) compared with short-acting decapeptyl (17.3%) or no gonadotrophin-releasing hormone agonist (GnRHa, 15.2%) treatments. However, the chances of implantation per embryo transferred being in excess of one in patients who became pregnant tended to be higher in non-GnRHa (23.5%) compared to buserelin- (16.4%) or decapeptyl- (13.3%) treated IVF cycles. Moreover, frozen--thawed embryos had a higher implantation rate (P less than 0.05) when originating from IVF cycles without GnRHa (11.7%) compared to GnRHa-treated cycles (buserelin, 4.3%; decapeptyl, 5.9%). It can be concluded that GnRHa associated with gonadotrophins produced embryos of a poorer aptitude for development than stimulation treatments without GnRHa. The clinical efficacy of GnRHa in IVF--ET cycles could be the result of an improved uterine receptivity to the transferred embryos.