Mastering the move: kinematic signatures of expertise in embryo transfer simulation

How does embryo transfer technique, assessed through a simulator validated by the American Society for Reproductive Medicine, vary according to procedural difficulty and practitioner expertise?

This observational prospective study was conducted from February to May 2024 in assisted reproductive technology centres in western France. Twenty-seven fertility specialists from six centres performed nine embryo transfer simulations at the University of Rennes, using a one-step approach across three pelvic models of increasing difficulty (A1, E1, C). Kinematic data from the simulator were analysed according to scenario difficulty and provider experience. Parameters included the catheter's linear velocity during introduction and, during ejection, the distance from the fundus, ejection speed, mean jerk and total duration.

The mean linear velocity of the catheter guide decreased with model difficulty (A1: 2.8 ± 1.4; E1: 2.1 ± 0.95; C: 2.1 ± 0.87 cm/s; P < 0.001). The mean fundus distance increased from 13 ± 5 mm (A1) to 18 ± 6 mm (E1) and 16 ± 7 mm (C) (P < 0.001). Average jerk values were 7046 ± 7822, 3641 ± 3028 and 3452 ± 3402 cm/s⁻³, respectively (P = 0.001). The ejection speed did not differ significantly (P = 0.844). The total duration increased with the difficulty (18 ± 8 s, 36 ± 25 s and 40 ± 51 s, respectively; P < 0.001). Practitioners with higher pregnancy rates showed slower catheter introduction and lower ejection speeds (P = 0.006 and P = 0.0002, respectively).

The embryo transfer kinematics varied with both procedural complexity and operator expertise. Slower, more controlled movements correlated with higher standardized pregnancy rates. Simulation appears valuable for identifying performance-linked metrics and refining training toward safer, more effective embryo transfer practices.