Fig. 2

Chemical pregnancy rate (a), clinical pregnancy rate (b), ongoing pregnancy rate (c), live birth rate (d), ectopic pregnancy rate (e), and early pregnancy loss rate (f) in FET following different endometrial preparation protocols. FET, frozen-thawed embryo transfer; NC, natural cycles; OS, ovarian stimulation; HRT, hormone replacement therapy. Multiple comparisons of pregnancy outcomes among groups were performed by multinomial logistic regression. Chemical pregnancy was defined as an elevated serum β-hCG level of more than 10 mIU/ml. Chemical pregnancy rate was defined as the number of chemical pregnancy divided by the number of embryo transfer cycle for each group. Clinical pregnancy was defined as a pregnancy documented by ultrasound at 6–8 gestational weeks that showed a gestational sac inside the uterus. Clinical pregnancy rate was defined as the number of clinical pregnancy divided by the number of embryo transfer cycle for each group. Ongoing pregnancy was defined as a pregnancy documented by ultrasound at 12 gestational weeks that showed the presence of fetal heartbeat. Ongoing pregnancy rate was defined as the number of ongoing pregnancy divided by the number of embryo transfer cycle for each group. Live birth was defined as the delivery of one or more infants with any signs of life after 28 gestational weeks. Live birth rate (% per embryo transfer cycle) was defined as the number of live birth divided by the number of embryo transfer cycle for each group. Ectopic pregnancy was defined as an embryo implanted outside the uterine. Ectopic pregnancy rate was defined as the number of ectopic pregnancy divided by the number of embryo transfer cycle for each group. Early pregnancy loss was defined as a pregnancy loss before 12 gestational weeks. Early pregnancy loss rate was defined as the number of early pregnancy loss divided by the number of clinical pregnancy for each group