To evaluate the effect of endometrial volume (EV) on the live birth rates (LBR)s in fresh or frozen embryo transfer (ET) cycles.

This is a prospective study including all women who underwent a fresh or frozen single blastocyst transfer between January 2017 and September 2018 in a university affiliated private hospital. Patients with advanced age (>42years), congenital uterine anomalies, endometrial or myometrial abnormalities, those with a difficult ET, those with only poor-quality blastocysts available for transfer, those in whom an optimal 3D TVUS image could not be obtained and those who were lost to follow-up were excluded. Endometrial volume was assessed using Virtual Organ Computer Aided Analysis program immediately prior to ET by two different observers using a standardized technique. The association of ET outcome and EV was evaluated by receiver operating characteristics (ROC) curve and logistic regression analysis.

A total of 142 patients were included in the final analysis. Patients were grouped according the EV percentiles (p); 5thp (1.7 mL), 10thp (2.2 mL), 25thp (2.9 mL), 50thp (4.3 mL) and >75thp (>5.3 mL) groups. ROC curve analysis was not predictive of LBRs, with an AUC (95 % CI) = 0.48 (0.38–0.58). There was no critical threshold, below which pregnancy was unlikely to occur. No significant association was observed between EV and any of the evaluated clinical outcomes.

When controlled for potential confounders, EV assessed by 3D TVUS is not a useful tool for predicting pregnancy in single blastocyst ET cycles.