A computational fluid dynamics modelling of maternal-fetal heat exchange and blood flow in the umbilical cord

Abstract

Human fetal thermoregulation, maternal-fetal heat exchange, and the role of the umbilical cord in these processes are not well understood. Ethical and technical limitations have restricted current knowledge to animal studies, that do not reflect human morphology. Here, we present the first 3-dimensional computational model of the human umbilical cord with finite element analysis, aiming to compute the maternal-fetal heat exchange. By modelling both the umbilical vein and the two umbilical arteries, we found that the coiled geometry of the umbilical artery, in comparison with the primarily straight umbilical vein, affects blood flow parameters such as velocity, pressure, temperature, shear strain rate and static entropy. Specifically, by enhancing the heat transfer coefficient, we have shown that the helical structure of the umbilical arteries plays a vital role in the temperature drop of the blood, along the arterial length from the fetal end to the placental end. This suggests the importance of the umbilical cord structure in maternal-fetal heat exchange and fetal heat loss, opening the way for future research with modified models and scenarios, as the basis for early detection of potential heat-transfer related complications, and/or assurance of fetal wellbeing.

Fig 1

An UC of 60cm total length was modelled (a). The UV was designed as a uniform straight tube, with two uniform UAs twisted over it (b). A sparse and a dense mesh (c) were selected.

Fig 2

Illustration of the gradual reduction of the temperature as the blood was moving from the input to the output (a). The more helical coils the velocity had to pass the more it reduced towards the output. The reduction of the velocity in the UV was lower (b).

Fig 3. For all the graphs the zero (0) on the x axis is the fetal end (UA input, UV output) and the 0.6m is the placental end (UA output, UV input).

The total length of the UC was 0.6m. The temperature drop in the UA, as the blood flowed from the fetus to the placenta is shown in the relevant graph below. It can be observed that the difference in the temperatures of UA and UV at 0m, was almost eliminated at the 0.6m. In comparison, although the reduction of average velocity was noticeable for both UV and UAs, it was not gradual. The pressure drop was significant in the UA, presenting an increase towards the output.