A standardized training allows achieving similar clinical pregnancy rates per top-quality euploid blastocyst transfer across operators.

Purpose: To evaluate the performance of different embryo transfer (ET) operators in a strictly controlled scenario minimizing potential confounders.

Methods: This single-center retrospective cohort study analyzed vitrified-warmed single euploid top-quality day-5 blastocyst transfers performed in non-obese women at the same IVF center by four equally trained clinicians using a standardized ET technique. These strict inclusion criteria allowed excluding all main confounders on the primary study outcome, namely clinical pregnancy rate (CPR) per ET across different operators. Endometrial preparation protocol, maternal age at transfer, parity, and the embryologist involved were assessed as putative further confounders.

Results: Out of 8663 ETs performed between January 2013 and December 2021, 421 first single euploid top-quality blastocyst transfers were included. No significant difference in ET outcomes was observed among clinicians. Multivariate logistic regression analysis confirmed no association between ET operators and CPR. The experience-defined as the sequential number of previous ETs conducted-did not involve any increase in the CPR.

Conclusions: The ET operator does not affect ET outcomes when subject to the same training and adopting a standardized ET protocol. As the performance does not increase with experience, the initial training is crucial to standardize the procedure across clinicians. In this regard, the CPR per euploid transfer can be considered a valuable Key Performance Indicator (KPI) for quality control purposes. Larger studies are required to build a consensus on competence and benchmark values to achieve.