Objective: To investigate the efficacies of three cycle regimens in women receiving FET with a history of CS: natural cycle (NC) treatment, hormone replacement therapy (HRT) and treatment with gonadotropin-releasing hormone agonist (GnRH-a) + HRT). Design: Retrospective cohort study. Setting: University-affiliated center. Population: Patients (N = 6,159) with a history of CS who fulfilled the inclusion criteria were enrolled in the study from January 2014 to December 2019. Methods: Reproductive outcomes of patients in the NC (n = 4,306) versus HRT (n = 1,007) versus GnRH-a + HRT groups (n = 846) were compared. Main Outcome Measure: The main outcome measure was the live birth rate per embryo transfer (ET). Results: The unadjusted odds of the miscarriage rate of singleton pregnancies were also significantly higher in the HRT-group compared with the NC-group (25.5% versus 20.4%, respectively). After adjusting for possible confounding factors, the early miscarriage rate and the miscarriage rate of singleton pregnancies remained significantly higher in the HRT-group than the NC-group. The clinical pregnancy rates in the NC-, HRT- and GnRH-a + HRT-groups of women with a history of CS was 48.8%, 48% and 47.1%, respectively, and the live birth rates were 37%, 34.1% and 35.7%, respectively. Conclusion(s): In women undergoing FET with a history of CS, HRT for endometrial preparation was associated with a higher early miscarriage rate, albeit after statistical adjustment for confounding factors. Funding: The National Science Foundation of China (81501328). Key Words: Caesarean section, endometrial preparation, frozen embryo transfer, miscarriage