Fluid dynamics during embryo transfer

Objective: To study fluid dynamics during ET. Design: Computational fluid dynamics were applied to calculate fluid velocity changes, dynamic pressure differences, and shear stress in the transferred load for the following injection speeds: 0.1, 1, 6, 12, and 20 m/sec. Setting: Academic research institute of mechanical engineering and reproduction biotechnology and private centers of reproductive medicine. Patient(s): None. Intervention(s): None. Main Outcome Measure(s): Fluid velocity, dynamic pressure, and shear stress during injection of the transferred load. Result(s): An increase of injection speed for the transferred load increased the shear stress, dynamic pressure, and velocity differences acting on the embryo. The narrowing of the catheter lumen diameter by 20% amplified the transferred fluid velocity by 78%. An embryo positioned in proximity to the catheter's wall was exposed to considerably higher shear stress, dynamic pressure, and velocity difference than an embryo in the center of the catheter's lumen. Conclusion(s): The transfer of an embryo should be conducted gently and with minimal injection speed. Any narrowing of the catheter lumen should be eliminated. Preferably the embryo should be kept far from the catheter's wall during injection of the transferred load. (Fertil Steril (R) 2011; 96: 324-7. (c) 2011 by American Society for Reproductive Medicine.)