The systole/diastole (S/D) flow velocity ratios in umbilical arteries (UAs) have been used to assess the health status of the feto-placental circulation, yet its connection to the morphology of UAs, specifically its coiling pattern remains unclear. Spiral flow induces unbalanced wall shear stress (WSS) distribution in UAs, and may contribute to the uneven arterial wall thickness, and the chirality. In this paper, we use a 3D computational fluid dynamics (CFD) technique to quantify the wall shear stress (WSS) in UA models of two configurations, i.e. at 0.17 and 0.50 spirals per centimeter, to represent normo- and hyper-coiling, respectively. For CFD simulations we use two different S/D ratios (3.02 and 5.70) revealed from the ultrasonography waveforms of a normal and an intrauterine growth restriction (IUGR) case. We found that more coils in the UA model enhanced WSS throughout a cardiac cycle (up to 24%) with the same inflow condition. In addition, time-averaged WSS are generally increased and more uneven in the hyper-coiling model. We suggest that the large WSS difference between the peak systole and end diastole (62% higher in the IURG case than the normal case) may induce uneven stenosis distribution at UAs, and contribute to UA chirality.

脐动脉 (UA) 的收缩/舒张 (S/D) 流速比已被用于评估胎儿 - 胎盘循环的健康状况，但其与 UA 形态的联系，特别是其盘绕模式仍不清楚。螺旋流在 UA 中引起不平衡的壁剪切应力 (WSS) 分布，并可能导致不均匀的动脉壁厚度和手性。在本文中，我们使用 3D 计算流体动力学 (CFD) 技术来量化两种配置的 UA 模型中的壁面剪应力 (WSS)，即每厘米 0.17 和 0.50 螺旋，分别表示正常和超螺旋. 对于 CFD 模拟，我们使用正常和宫内生长受限 (IUGR) 病例的超声波形显示的两种不同的 S/D 比（3.02 和 5.70）。我们发现 UA 模型中更多的线圈在相同的流入条件下增强了整个心动周期的 WSS（高达 24%）。此外，在超卷曲模型中，时间平均 WSS 通常会增加并且更加不均匀。我们认为峰值收缩期和舒张末期之间的大 WSS 差异（IURG 病例比正常病例高 62%）可能导致 UA 的狭窄分布不均匀，并有助于 UA 手性。