The ART-ET screening tool: an easy-to-use non-invasive screening method to predict difficult embryo transfers in advance.

Study question: What is the diagnostic performance of the ART-ET screening tool, an easy-to-use non-invasive screening tool for prediction of difficult embryo transfers?

Summary answer: A simple scoring of transvaginal ultrasound examination of the cervical canal can predict difficult embryo transfers with high specificity, positive likelihood ratio, and accuracy; the inclusion of cervical position and history of cesarean without a vaginal delivery improved predictive performance.

What is known already: Difficult embryo transfer procedures are associated with significantly lower clinical pregnancy and live birth rates, and some interventions may facilitate an anticipated difficult embryo transfer.

Study design, size, duration: A diagnostic test study prospectively conducted on 239 single euploid blastocyst transfer procedures between March and December 2023. The sample size was calculated to include about 20 difficult transfer procedures. Physicians conducting the transfers were blinded to screening results.

Participants/materials, setting, methods: The study was conducted in two tertiary-level private assisted reproduction centers. The ART-ET Screening tool collected information on patients' body mass index, obstetric history, cervical position, external cervical ostium appearance, and ultrasound examination of the cervical canal. A difficult embryo transfer was defined if one or more of the following occurred during the procedure; use of a malleable obturator to insert the guiding catheter until the internal ostium, use of a forceps to pull the cervix, if there were blood in the transfer catheter following the procedure, if the transfer catheter needed to be reloaded, and if the physician found the procedure difficult.

Main results and the role of chance: Ongoing pregnancy rates were 47.6% vs 59.6% after a difficult and easy embryo transfer. With a difficult embryo transfer prevalence of 8.8%, screening score including cervical position, visibility and the length of cervical canal, and obstetric history had the best diagnostic performance with sensitivity of 33.3% (14.59-56.97%), specificity of 99.5% (97.47-99.99%), positive likelihood ratio of 72.67 (9.38-562.73), negative likelihood ratio of 0.67 (0.49-0.91), and an accuracy of 93.7% (89.86-96.45%) for predicting difficult embryo transfers. The simpler cervical ultrasound score also had a good diagnostic performance with a sensitivity of 28.6% (11.28-52.18%), specificity of 98.2% (95.37-99.50%), positive likelihood ratio of 15.57 (4.77-50.84), negative likelihood ratio of 0.73 (0.55-0.95), positive predictive value of 60.0% (31.46-83.03%), negative predictive value of 93.5% (91.59-94.93%), and an accuracy of 93.5% (91.59-94.93%).

Limitations, reasons for caution: The diagnostic performance of the proposed ART-ET Screening tool would depend on the prevalence of difficult embryo transfers in a clinic. How much the scoring system can decrease difficult embryo transfers and improve live birth rates need to be determined in further studies.

Wider implications of the findings: Anticipation of a difficult transfer can help to adjust patient expectations and to take appropriate measures in advance.

Study funding/competing interest(s): No funding was received for the study. None of the authors have any competing interests associated with the present study.

Trial registration number: NCT05701072.