Endometrial compaction can improve assisted reproductive technology outcomes in frozen-thawed embryo transfer cycles using hormone replacement therapy: A cross-sectional study

Background: Endometrial compaction (EC) is an ultrasound evaluation method that may predict assisted reproductive technology outcomes. Objective: This study aimed to assess the impact of EC on assisted reproductive technology outcomes in frozen embryo transfer cycles with hormone replacement therapy. Materials and Methods: In this cross-sectional study, 100 women who underwent first or second frozen embryo transfer cycle at Yazd Reproductive Sciences Institute, Yazd, Iran from June to October 2024 were included. Endometrial thickness was compared between the day of starting progesterone and embryo transfer day. Then participants were divided into 2 groups, no compaction and compaction group. Biochemical, clinical, and ongoing pregnancy rates (OPR) were assessed between the 2 groups. Results: Statistically significant differences were observed in biochemical, clinical, and OPR between the compaction and no compaction groups. Logistic regression analysis demonstrated significantly higher pregnancy rates in EC 10–15% and > 15%. We found a significant influence of EC 10–15% (p = 0.02, p = 0.01, p = 0.01), and EC > 15% (p = 0.002, p = 0.001, and p = 0.002) on biochemical, clinical, and OPR, respectively. Conclusion: EC after progesterone administration in hormone replacement therapy-frozen embryo transfer cycles can increase biochemical, clinical, and OPR. The percentage of EC changes also influence the outcomes of these cycles.