Endometrial thickness/volume and uterine peristalsis in adenomyosis patients undergoing frozen embryo transfer to predict pregnancy outcomes: A retrospective study

To analyze the significance of endometrial thickness (EMT), endometrial volume and uterine peristalsis (UP) for forecasting the pregnancy outcome of patients with adenomyosis (ADM) undergoing frozen embryo transfer (FET). Women diagnosed with ADM between February 15, 2017, and March 15, 2025 from one tertiary care center in southwest China, were retrospectively included. There were 111 cases in the pregnant group, whereas 60 in the nonpregnant group. EMT, endometrial volume and UP on the endometrial transformation day and 1 day before embryo transfer (ET) during the FET cycle between 2 groups were compared. No significant differences could be observed in EMT or endometrial volume on the endometrial transformation day or 1 day before ET in 2 groups (P = .288, P = .461, P = .913, P = .239, separately). The nonpregnant group had an increased UP frequency relative to the pregnant group on the endometrial transformation day (2.28 ± 1.32 vs 1.29 ± 0.95, P = .001) and 1 day before ET (1.82 ± 0.97 vs 1.36 ± 0.94, P = .003). Binary logistic regression analysis revealed that EMT and endometrial volume at 2 time points were not the independent risk factors affecting the FET outcome (odds ratios: 1.112, 95% confidence interval [CI]: 0.888-1.393, P = .355; 1.140, 95% CI: 0.834-1.558, P = .411; 0.902, 95% CI: 0.717-1.136, P = .381; 1.201, 95% CI: 0.937-1.538, P = .149). As suggested by receiver operating characteristic curve analysis, the area under the curve values of EMT and endometrial volume on the endometrial transformation day were 0.461 and 0.458, while those 1 day before ET were 0.501 and 0.444 separately. Nonetheless, UP on the endometrial transformation day was identified to be a factor independently affecting the clinical pregnancy probability of ADM patients, and the odds ratio was 0.323 (95% CI:0.187-0.557). Area under the curve values of UP were 0.720 and 0.627 on the endometrial transformation day and 1 day before ET separately. Neither EMT nor endometrial volume can predict the pregnancy outcome of ADM patients undergoing FET. Uterine peristalsis in the transplantation process serves as an indicator for pregnancy outcome.