ABSTRACT
OBJECTIVE: To compare the clinical pregnancy rates between two types of endometrial preparation protocolsnatural cycle（NC）and hormone replacement cycle（HRT）-in patients with thin endometrium in the frozen-thawed embryo transfer（FET）cycles.METHODS: From January 2012 to December 2018,FET patients with endometrial thickness ≤7 mm on the day of human chorionic gonadotropin（h CG）trigger in Reproductive Medicine Center of the First Affiliated Hospital of Sun Yat-sen University were selected as research subjects.According to the endometrial preparation protocols,they were divided into NC group and HRT group.Totally 117 pairs were successfully matched using the propensity score matching method.The matching variables were age,embryo type and number of transferred embryos,and the embryo implantation rate and clinical pregnancy rate of the two matched groups were compared.RESULTS: There was no significant difference in embryo implantation rate（36.47% vs. 39.03%）or clinical pregnancy rate（44.40% vs. 52.10%）between NC group and HRT group（P> 0.05）.CONCLUSION: NC group and HRT group had similar pregnancy rate in patients with thin endometrium in FET cycles.Individualized protocols can be adopted according to the characteristics of patients with thin endometrium.