Simulations of Embryo Transfer after In Vitro Fertilization

Osnat Eytan1, Ariel Jaffa1,2, David Elad2

1 Tel Aviv Sourasky Medical Center and 2 Tel Aviv University

Embryo transfer (ET) is the last stage of extracorporal fertilization at which embryos generated in the laboratory are returned to the uterus for development of a natural pregnancy. It is considered to be a major obstacle for embryo implantation, which is responsible for the low rate (<25%) of success of IVF procedures.

A laboratory setup was developed in order to mimic the procedure of ET into the non-pregnant uterus. A catheter loaded with alternating air and colored liquid, which represents the transferred matter with the embryos, was placed within a transparent model of the uterine cavity. The transfer procedure was simulated using a computer-operated syringe. The spreading of the colored liquid within the uterine cavity was recorded by a digital video camcorder for analysis of the embryos transport pattern.

The results indicated that injection of the liquid-air loading of the catheter into the uterus formed an air bubble, which blocked the transport of the transferred liquid towards the fundus (see video-1). The distribution of the transferred matter within the uterine cavity was determined for different air volumes, different combinations of the liquid-air sequences and several viscosity ratios between the transferred liquid and the uterine fluid. The study suggested that the catheter load should contain minimal volumes of air in order to enhance the embryos’ chances to reach the site of implantation.

VIDEO-1

A computational model was developed to simulate ET within the uterine cavity by a fluid-filled catheter inserted into a two-dimensional channel with oscillating walls. The intrauterine transport was controlled by the unsteady continuity and Navier Stokes equations for an incompressible fluid with constant viscosity. Uterine peristalsis was imposed by periodic motility of the uterine walls (see video-2). Simulations of embryos transport after injection of the matter showed that the speed of injection dictated their transport within the uterine cavity. Transfer at excessively high injection speeds may lead to ectopic pregnancies, while uterine peristalsis affects transverse dispersion only during injection at low injection speeds. The presence of the catheter within the uterus does not affect flow patterns downstream of its tip.

VIDEO-2

References

  1. Eytan O, Elad D, Zaretsky U, Jaffa AJ. A glance into the uterus during in vitro simulation of embryo transfer. Human Reproduction, 19: 562-569, 2004.
  2. Yaniv S, Elad D, Jaffa AJ, Eytan O. Biofluid aspects of embryo transfer. Annals of Biomedical Engineering, 31: 1255-1262, 2003 (also published in: Virtual Journal of Biological Physics Research, 9(6), November, 2003).