RESUMO
BACKGROUND: The use of frozen embryo transfer (FET) is increasing worldwide in the treatment of infertility by in vitro fertilization. Different methods of endometrial preparation for FET have been suggested. OBJECTIVE: The aim of this study was to compare the pregnancy outcomes after treatment with letrozole and those after treatment with the combination of gonadotropin-releasing hormone (GnRH) agonist and estradiol in FET. MATERIALS AND METHODS: This randomized controlled trial study was conducted on 142 infertile women with a history of previous FET failure. Participants were randomly assigned to two groups (n = 71 each). The GnRH group received 500 µg of buserelin plus 4mg estradiol (which increased to 8 mg if endometrial thickness was less than 5 mm), and the letrozole group received 5 mg of letrozole plus 75 IU of recombinant human follicle-stimulating hormone). At least two high-quality embryos were transferred to each subject in both groups. The outcome measures were clinical pregnancy rate and fetal heart rate detection. RESULTS: Subjects in the study groups had similar demographic characteristics and baseline clinical condition. Mean endometrial thickness in the letrozole and GnRH agonist groups were 8.90 ± 0.88 mm and 8.99 ± 0.85 mm, respectively (p = 0.57). The number of positive results of the beta human chorionic gonadotropin test and detection of fetal heartbeat were not significantly different between the groups (p > 0.05). CONCLUSION: The administration of letrozole and GnRH may produce similar pregnancy outcomes in FET.
