Introduction: Endometrial preparation is an important step in frozen embryo transfer. Although different protocols are commonly used, current evidence has not established the clear superiority of one method over the others. This present study was conducted with aim to compare the evaluated post-transfer indicators following different endometrial preparation cycles in women undergoing frozen embryo transfer.
Methods: This retrospective analytical study was conducted at Mahdieh Hospital, Tehran, Iran, during 2022–2024. Medical records of 330 women undergoing frozen embryo transfer were reviewed. Patients included 273 women in the estrogen and progesterone group, 43 in the GnRH agonist plus estrogen and progesterone group, and 14 in the letrozole ovulation induction group. Demographic data, cycle characteristics, and evaluated post-transfer indicators were extracted from patients’ records and analyzed. Data analysis was done using SPSS statistical software (version 22) and Kruskal-Wallis test. P<0.05 was considered significant.
Results: The mean age (p=0.001) and body mass index (p=0.01) were significantly higher in the letrozole group. The mean anti-mullerian hormone was higher in the estrogen and progesterone group (p=0.02). The number of embryos transferred in the letrozole group (p=0.04) and the number of embryo transfers in the GnRH agonist group (p=0.002) were higher. There was no significant difference among the three groups in terms of egg quality (p=0.58) and endometrial thickness (p=0.78). Also, there was no significant difference among the three groups in β-hCG positivity (p=0.23), pregnancy continuation until the 12^th week (p=0.24), and ectopic pregnancy (p=0.90).
Conclusion: In this study, no significant differences were observed among the GnRH agonist plus estrogen and progesterone, estrogen and progesterone, and letrozole protocols in terms of the evaluated post-transfer indicators, including β-hCG positivity, pregnancy continuation up to 12 weeks, and ectopic pregnancy. The choice of endometrial preparation protocol may be individualized based on the patient’s clinical condition and physician’s judgment.