Understanding prenatal brain sparing by flow redistribution based on a lumped model of the fetal circulation

Intrauterine Growth Restriction due to placental insufficiency leads to cardiac dysfunction in utero which can persist postnatally. Brain sparing by flow redistribution is an adaptive mechanism used by the restricted fetus to ensure delivery of oxygenated blood to the brain. The quantification of reversed flow in the aortic isthmus is used in clinical practice to detect signs of brain sparing. Two parameters are used to quantify reversed flow: pulsatility index and isthmic flow index. We developed a simplified 0-D lumped model of the fetal circulation to simulate brain-sparing for better understanding this compensatory mechanism and its influence on the mentioned parameters. We were able to reproduce the clinical phenomenon and to quantify the effect of brain sparing on pulsatility and isthmic flow indexes. Therefore, our model seems to be a good approximation of the fetal circulation and offers potential to study hemodynamic changes in intrauterine growth restricted fetuses.