Hemodynamic analysis of arterial blood flow in the coiled umbilical cord.

The most significant anatomical structure of the umbilical cord is its level of coiling. The coiled geometry of the umbilical cord largely affects umbilical blood flow that is vital for fetus's well-being and normal development. In this study, we developed a computational model of steady blood flow through the coiled structure of an umbilical artery. The results showed that the driving pressure for a given blood flow rate is increasing as the number of coils in cord structure increases. The driving gradient pressures also vary with the pitch that dictates the coils' spreading. The coiled structure is resulting in interwoven streamlines along the helix and wall shear stresses (WSS) with significant spatial gradients along the cross-sectional perimeter anywhere within the helical coil. These gradients may have an adverse effect on the development of the fetus cardiovascular system in cases with over coiling (OC) or under coiling (UC) characteristics. The number of coils does not affect the distribution and levels of WSS. However, when the coils are more spread (eg, larger pitch number), the maximal WSS is significantly smaller. Cases with twisted and OC cords seem to yield very large values and gradients of WSS, which may place the fetus into high risk of abnormal development.