Evaluation of the embryo transfer protocol by a laboratory model of the uterus

Objective: To investigate the dispersion of transferred matter within a uterine laboratory model during and after embryo transfer (ET) as a function of uterine position, catheter placement, and injection speed. Design: Experimental setup. Setting: Reproductive bioengineering laboratory. Patient(s): N/A. Intervention(s): N/A. Main Outcome Measure(s): Laboratory simulations of ET into a rigid transparent uterine model. The catheter was loaded with sequences of liquid and air as in the clinical setting. Experiments were conducted for different inclinations of the uterine model, various transfer speeds of the catheter load, and placement of the catheter tip near and remote from the fundus. Result(s): Dispersion of the transferred matter depended on the position of sagittal cross-section of the uterine cavity with respect to the horizon. The air bubbles were pulled up by buoyant forces toward the highest point of the cavity (e.g., the fundus) and thereby dragged behind them the transferred media with the embryos. Placement of the catheter tip near the fundus appeared to transfer the embryos into the tube when transfer was performed at fast speeds, possibly leading to ectopic pregnancies. Conclusion(s): Fundal level of the uterine cavity, location of the catheter tip, and transfer speed determine the potential for embryo implantation. Adjustment of ET protocol to individual patient anatomy is recommended.