Pregnancy outcomes of 4 endometrial preparation protocols in adenomyosis patients with thin endometrium during frozen embryo transfer: a retrospective cohort study

Introduction: This study aimed to compare the pregnancy outcomes of different endometrial preparation protocols in patients with adenomyosis and thin endometrium during frozen embryo transfer. Methods: The study, which was conducted at the Reproductive Hospital Affiliated to Shandong University, included 236 patients with adenomyosis and thin endometrium who underwent frozen embryo transfer between January 1, 2011, and December 12, 2022. The pregnancy outcomes and maternal and infant complications among the 4 groups were further compared. Results: These patients with adenomyosis and thin endometrium were divided into 4 groups based on the endometrial preparation protocols used: natural cycle treatment (n=53), hormone replacement therapy group (n=73), gonadotropin-releasing hormone agonists + hormone replacement therapy group (n=49), and ovarian induction group (n=61). The demographic, cycle, and embryologic characteristics were similar between groups. The livebirth rates (P=0.29), full-term pregnancy rates (P=0.55), preterm pregnancy rates (P=0.33), clinical pregnancy rates (P=0.77), biochemical pregnancy miscarriage rates (P=0.28), early miscarriage rates (P=0.16), and late miscarriage rates (P=0.69) were comparable among 4 groups. In addition, there were no significant differences in maternal and infant complications. Conclusion: The pregnancy outcomes of frozen-embryo transfer among 4 endometrial preparation protocols in patients with adenomyosis and thin endometrium were comparable, indicating no significant disparities. In addition, no noteworthy variations were observed in terms of maternal and infant complications in these patients.