Anatomical and hemodynamic changes in the vascular bed of umbilical cord during intranatal period

Objective: to analyze anatomical and hemodynamic transformations in the vascular bed of the umbilical cord during labor using computer modeling of physiological processes and the associated change in the external pressure gradient. Materials and Methods. The first stage of the study included 3D modeling using the Ansys Fluent 2021 software of a single straight umbilical artery under external pressure of 120 mmHg. The second stage involved 3D modeling of umbilical vessels in the organ complex surrounded by embryonic mucous connective tissue (EMCT) under similar external pressure. Results. In an isolated straight umbilical artery, when exposed to external pressure, the blood flow velocity increased by 85.5%, and intravascular pressure by 38.5%. In 3D modeling of the entire umbilical cord under similar pressure, the blood flow velocity in the umbilical arteries increased by 20% and intravascular pressure increased by 8%, while the blood flow velocity in the umbilical vein increased by 24% and the intravascular pressure by 10%. The cross-sectional area of the EMCT, umbilical arteries, and vein did not change, despite the external deformation of the umbilical cord, vascular wall and changes in the lumen of the vessels. Conclusion. Anatomical and hemodynamic parameters in the umbilical vessels during the intranatal period undergo transformations of varying severity, consisting in an increase of intravascular blood flow velocity and pressure, deformation of the umbilical cord and vascular wall, and narrowing of the lumen of the vessels, while maintaining the cross-sectional area of the umbilical cord and its vessels against the background of external pressure.