Abstract:Abstract: Objective To compare the clinical outcomes of frozen-thawed embryo transfer in luteinized unrupture follicle (LUF) cycle and the natural cycle. Methods Totally 1,380 natural cycles of frozen-thewed embryo transfer which were performed in the Reproductive Medical Center of the Second People's Hospital of Nanning, Guangxi from July 2013 to June 2015 were retrospectively analyzed. The 1,380 cycles, including 174 LUF cycles and 1,206 natural cycles, were divided into cleavage stage embryo group and blastocyst group. The levels of E2 and LH on the day before LUF or ovulation, endometrial thickness, biochemical pregnancy rate, implantation rate, clinical pregnancy rate and early abortion rate were compared. Results In the cleavage stage embryo group, the level of LH on the day before LUF was statistically lower than that on the day before ovulation [(33.78 ± 16.20) mIU/ml vs (39.69 ± 17.18) mIU/ml, P < 0.05]. Meanwhile, in the blastocyst group, the level of LH on the day before LUF was also statistically lower than that on the day before ovulation [(32.84 ± 17.91) mIU/ml vs (40.27 ± 17.28) mIU/ml, P < 0.05]. But there was no obvious statistical diffe-rence in endometrial thickness, biochemical pregnancy rate, implantation rate, clinical pregnancy rate or early abortion rate between the two groups (P > 0.05). Conclusions For frozen-thewed embryo transfer, LUF cycle with adequate luteal phase support can achieve a pregnancy outcome similar to the natural ovulation cycle.