Intra-uterine fluid motion due to myometrial contractions: A mechanism for embryo transport

The uterine wall contractions in non-pregnant women were analyzed to determine the mechanisms of intra-uterine embryo transport. Trans-vaginal ultrasound images of endometrial motility were used and intra-uterine flow was simulated by a model of viscous flow. The myometrial contractions were responsible for intra-uterine fluid motion. The structural organization of myometrial muscle fibers may induced asymmetric and non-periodic uterine wall motility. As a result, the embryo may be transported within the upper region of the uterine cavity in a chaotic trajectory until it reaches an appropriate implantation site at the wall. In other cases, it may reach a non-optimal implantation site far away from the fundus, which will end with a miscarriage.