Which endometrial preparation protocol provides better pregnancy and perinatal outcomes for endometriosis patients in frozen-thawed embryo transfer cycles? A retrospective study on 1413 patients

OBJECTIVE: To determine the optimal endometrial preparation protocol for a frozen embryo transfer in patients with endometriosis. DESIGN: Retrospective cohort study. SETTING: Tertiary care academic medical center. PATIENT(S): One thousand four hundred thirteen patients with endometriosis who underwent oocyte aspiration from 2015 to 2020 and frozen embryo transfer from 2016 to 2020 and received natural cycle, hormone replacement treatment with or without GnRHa pretreatment endometrial preparation. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Clinical pregnancy rate, live birth rate, miscarriage rate, multiple pregnancy rate, biochemical pregnancy rate and ectopic pregnancy rate. Singleton live births were assessed for perinatal outcomes and obstetric complications. RESULT(S): There were no differences in clinical pregnancy outcomes or prenatal outcomes among the three commonly used endometrial preparation protocols for frozen embryo transfer cycles in patients with endometriosis. Results remained after screening variables using univariate logistic regression into multivariate logistic regression. No advantages or disadvantages were found among the three endometrial preparation protocols in patients with endometriosis. CONCLUSION(S): Natural cycle, hormone replacement cycle, or hormone replacement treatment with GnRHa pretreatment showed no superiority or inferiority in pregnancy and perinatal outcomes in patients with endometriosis. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13048-023-01095-4.