Abstract: Objective： To compare the level of luteinizing hormone and the outcome of in vitro fertilization-embryo transfer （IVF-ET） conducted with prolonged protocol and long protocol on infertile patients with moderate or severe endometriosis. Methods：A retrospective analysis was performed. Those 69 infertile patients （69 cycles） with moderate or severe endometriosis were treated with long-term gonadotropin-releasing hormone agonist（GnRHa） down-regulation for 3 months following IVF-ET treatment. Those patients were divided into 2 groups based on different start-time of the controlled ovarian hyperstimulation（COH） protocol，27 patients were in the general ultra-long-protocol group（control group） who received Gn treatment on the 28th day after the last injection day；42 patients were in the contraceptives transition protocol group （OC group） who received oral contraceptives 1 tablet per day on the 28th day after the last injection day and injected GnRHa（Diphereline） on the 17th day. All patients received gonadotropin（Gn） treatment 14 days after the GnRHa 1.25-1.88 mg injection. Results：The OC group had significantly higher implantation rate and clinical pregnancy rate than control group（χ2=5.518，P=0.019； χ2=4.010，P=0.045）. Conclusions：The controlled ovarian hyperstimulation applied with contraceptives transition long protocol after GnRHa down-regualtion is a better way for those patients with emdometriosis. It is easy to master the start time of Gn and alleviate the excessive inhibition of GnRHa for pituitary. This method can obtain good pregnancy outcome.

Key words: Endometriosis, Gonadotropin-releasing hormone, Contraceptives, oral, Fertilization in vitro, Embryo transfer