Hemodynamic analysis on the umbilical cord with different coiling and nuchal cord conditions: A computational model-based study

The umbilical cord is a vital pathway for the fetus, which can bring oxygen/nutrition and take away waste products to maintain normal growth. Clinical studies found that abnormal coiling and nuchal cord conditions of the umbilical cord may be associated with fetal growth restriction. Although the hemodynamic environment due to the abnormal morphology is suspected to account for the abnormal growth, the specific influence of the abnormal coiling and nuchal cord conditions on the hemodynamics remains not fully understood. In this context, this study aims to investigate the hemodynamic effects of the variation of umbilical coiling index (UCI) and nuchal cord conditions in order to better address the issue. For this purpose, the computational model of a normal umbilical cord was constructed based on the ultrasound-measured geometrical parameters and blood flow velocity. On this basis, a series of computational models with lower/higher UCI and with/without nuchal cord were then constructed, which were used in the hemodynamic analysis and comparison. Results showed that (1) both abnormal UCI (lower and higher) and nuchal cord conditions significantly altered the hemodynamic environment; (2) the variations of UCI resulted in inverse tendencies between oscillatory shear index (OSI) and relative residence time (RRT); and (3) nuchal cord had minor impact on most hemodynamic variables, such as wall shear stress and RRT, but increased the area of higher OSI. These findings clarified the influence of different coiling and nuchal cord conditions on the hemodynamic environment of the umbilical cord, which would provide more insights into fetal growth restriction.