The Iranian Journal of Obstetrics, Gynecology and Infertility

The Iranian Journal of Obstetrics, Gynecology and Infertility

Evaluation and Comparison of Different Endometrial Preparation Cycles for Frozen Embryo Transfer: A Retrospective Study

Document Type : Original Article

Authors
Seyyedeh Atefeh Kashani 1
Tayebeh Esfidani 2
Amene Abtahian 1
1 Fellowship of Infertility, Department of Obstetrics and Gynecology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
2 Assistent Professor, Department of Obstetrics and Gynecology, Fellowship of Infertility, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
10.22038/ijogi.2026.94430.6673
Abstract
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 12th 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.
Keywords
Endometrium
Frozen Embryo Transfer
GnRH Agonist
Letrozole
Pregnancy Outcome
Subjects
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The Iranian Journal of Obstetrics, Gynecology and Infertility
Volume 29, Issue 4
June 2026
Pages 23-30