Unraveling Endometrial Abnormalities: A Comprehensive Ultrasound Assessment During Frozen Embryo Transfer (FET) Maturation Cycles.

Objective: To retrospectively analyze the ultrasonographic endometrial features of patients undergoing endometrial maturation for FET and correlate them with pregnancy outcomes.

Methods: This is a retrospective study of endometrial echo images taken from women aged 18-45 planning a frozen embryo transfer (FET) at the Cleveland Clinic between April 1, 2021, through September 30, 2021. Endometrial assessment was performed via transvaginal ultrasound during endometrial maturation for planned FET. Abnormal endometria were diagnosed by the presence of polyps, cystic lesions, heterogeneous morphology (coexisting hypo- and hyperechoic areas), and homogeneous (non-trilaminar) morphology. Normal endometria were trilaminar and lacked the abnormalities of interest. Outcome measures were failed conception, early pregnancy loss/biochemical pregnancy, and ongoing pregnancy. We performed t-test comparison for continuous variables and chi-square test for the categorical variables (R statistical program version 4).

Results: Exactly 128 endometrial echoes met inclusion criteria for analysis. Of those included, 53 (41.4%) were abnormal endometrium (AE) and 75 (58.5%) were normal endometrium (NE) and all patients underwent embryo transfer. Demographic characteristics were similar between the groups, including endometrial thickness and BMI. Mean age was 36.3 and 33.8 in the AE and NE groups, respectively (P = .001). After FET, 67.7% (n = 42) of the ongoing pregnancies were from the NE group versus 32.3% (n = 20) from the AE group. After adjusting for confounding factors like age, BMI, utilization of PGT-A, and endometrial thickness, proportional odds logistic regression demonstrated that the likelihood of an abnormal endometrium being associated with a poor pregnancy outcome is 12.06 times greater compared with a normal endometrium.

Conclusion: In preparation for FET, the presence of any kind of endometrial abnormalities at ultrasound before starting progesterone supplementation had a significant correlation with poor cycle outcomes, and conception rates were decreased by >50%. This study underscores the clinical importance of ultrasound in the evaluation of the endometrium and prediction of FET cycle outcomes.