Abstract: Objective：To compare the clinical outcomes of two protocols, the classical gonadotropin releasing hormone antagonist (GnRHA) protocol and the new GnRH agonist (GnRHa) long protocol, in those infertile patients with PCOS underwent in vitro fertilization-embryo transfer (IVF-ET) cycles, in order to explore the feasibility protocol with fewer complications. Methods： The infertile women with PCOS underwent IVF-ET in our center from January 2015 to September 2017 were respectively analyzed. A total of 240 cycles were divided into the GnRHA protocol group (GnRHA group, 90 cycles) and the GnRHa long protocol group (GnRHa group, 150 cycles). The clinical outcomes were compared between the two groups, including the gonadotropin duration, the number of retrieved oocyte, the number of 2PN fertilized egg, the fertilization rate, the number of usable embryos, the number of good quality embryos, the pregnancy rate of once ET and the rate of ovarian hyperstimulation syndrome (OHSS). Results：The day of drug-use of the GnRHA group was lower than that of the GnRHa group (Z=－11.230, P=0.000). There were no statistical differences in the number of 2PN fertilized egg, the fertilization rate, the number of usable embryos and the number of good quality embryos (both P＞0.05). The difference in the pregnancy rate of once ET (including fresh and thawed transplants) between the two groups was not significant (P＞0.05). There were 11 cases of severe OHSS in the GnRHa group and 1 case in the GnRHA group ( χ2=4.340, P=0.037). Conclusions：The pregnancy rates of once ET (including fresh and thawed transplants) in two protocols were not significantly different, however the rate of middle and severe OHSS in the GnRHA group was lower. The GnRHA protocol, without adjustment and with the reduced economic pressures and complications, and with the same pregnancy rate of GnRHa long protocol, may be tried in those infertile patients with PCOS underwent the IVF-ET treatment using freeze-thawed embryos.

Key words: Polycystic ovary syndrome, Infertility, female, Ovulation induction, Reproductive techniques, assisted