Endometrial Thickness Change in Response to Progesterone is Associated with Ongoing Pregnancy Rate in Women with Treated Intrauterine Adhesion - A Prospective Cohort Study.

Objective: This study aimed to investigate whether endometrial thickness (EmT) change prognosticates the ongoing pregnancy rate (OPR) in hormonally prepared frozen-thawed embryo transfers (FETs) in women with treated intrauterine adhesion (IUA). Methods: We prospectively examined 261 FET cycles in women with IUA. Ultimately, 156 patients were included in the final analysis. The primary outcome was OPR. The association between the EmT change ratio and OPR, as well as the relationship between the EmT change and serum hormone concentration, was analyzed. Results: The intraclass correlation coefficient for repeated EmT measurements was 0.944 (95% CI: 0.933-0.954, P < 0.001). Subdividing by the expansion cutoff from 5% to 15%, the 10% expansion group had the highest OPR with optimal sensitivity and specificity. Regarding the baseline characteristics, there were no statistically significant differences between the two groups. Nevertheless, the OPR increased significantly in cycles with endometrial expansion ≥ 10% compared to those with no expansion (55.3% vs 26.3%, P=0.001). The difference was still significant after adjustment between the two groups (adjusted OR, 3.74; 95% CI 1.68-8.34, P=0.001). No correlation was found between the EmT change and serum hormone concentrations. Conclusion: Endometrial expansion was significantly correlated with higher OPR in women with treated IUA in the hormonal protocol for FET.