Abstract: Objective: To investigate the effects of three kinds of endometrial preparation (normal hormone replacement,half- and full-dose of long-acting gonadotropin-releasing hormone agonist (GnRH-a) down-regulation combined with hormone replacement) on the pregnancy outcomes in the frozen-thawed embryo transfer (FET) cycle in the patients with endometriosis(EMT),adenomyosis or repeated implantation failure (RIF)for unknown reasons, and to provide a basis for the selection of clinical endometrial preparation method.Methods: A total of 191 patients with EMT,adenomyosis or RIF for unknown reasons underwent FET treatment were selected.The patients were divided into normal hormone replacement group(n=63),half-dose GnRH-a group(n=61) and full-dose GnRH-a group(n=67) according to the endometrial preparation method.The clinical data of patients in each group such as age,body mass index(BMI),duration of infertility,the number of embryo transfer cycles,the number of embryos transferred,the endometrial thickness on the day of conversion and transplantation,the rate of high-quality embryos transferred,the intrauterine clinical pregnancy rate and the embryo implantation rate were analyzed retrospectively and compared.Results: There were no significant differences of the general clinical data of the patients in FET cycles in three groups such as age,BMI,duration of infertility,the number of embryo transfer cycles,the number of embryos transferred,the endometrial thickness on the day of conversion and transplantation,and the rate of high-quality embryos transferred(P>0.05);the intrauterine clinical pregnancy rate and the embryo implantation rate of the patients in full-dose GnRH-a group and half-dose GnRH-a group were significantly higher than those of the patients in normal hormone replacement group(χ² = 9.000,χ² =7.917, P<0.05), but there were no statistically significant differences between half-dose GnRH-a group and full-dose GnRH-a group (P>0.05).Conclusion: In the FET cycles of the patients with EMT, adenomyosis or RIF for unknown reasons, hormone replacement after down-regulation of GnRH-a can effectively improve the pregnancy outcome of FET.The pregnancy outcomes of full-dose and half-dose of long-acting GnRH-a are relatively similar, and half-dose long-acting GnRH-a is more conducive to reduce the financial burden of the patients,and it is a ideal choice for endometrium preparation protocol in FET cycle.

Key words: frozen-thawed embryo transfer, endometrium preparation protocol, gonadotropin releasing hormone agonist, down-regulation, pregnancy outcome