Evaluation of a strategy for difficult embryo transfers from a prospective series of 2046 transfers

Structured Abstract Objective To evaluate an embryo transfer strategy for difficult transfers (DiTs). Design Prospective, nonrandomized, observational, cohort study Setting A hospital fertility center in France. Patients Data were collected on all embryo transfers conducted using the strategy between February 2014 and February 2020. Interventions Anatomical characteristics that could cause DiT were identified by transvaginal ultrasound and the catheter was adapted accordingly. Transfer was guided by transvaginal ultrasound. After passage through the cervix, a rest period was introduced to allow any contractions to stop before embryo deposition in the uterus. Main outcome measures The primary criterion was the percentage of pregnancies per transfer (P/T) following an easy transfer (EaT) or a DiT. The secondary criteria included the anatomical causes of DiT and patient levels of discomfort. Results Of 2046 transfers, 257 (12%) were DiTs: minor difficulties (n = 152; 7.4%), major difficulties (n = 96; 4.7%), very significant difficulties (n = 7; 0.3%) or impossible (n = 2; 0.1%). The most common causes of DiTs were endocervical crypts (54%), tortuous cervical canal (36%) and marked uterine anteversions (30%). Several causes were often responsible for DiTs. There was no significant difference in P/T between the EaTs (n = 1789, 41%) and all degrees of DiT (n = 257, 37%). There was also no difference between the EaT and DiT groups in the level of patient-reported discomfort. Conclusions This study demonstrated that an adapted embryo transfer strategy, monitored by transvaginal ultrasound, led to similar pregnancy rates regardless of whether transfer was easy or difficult.