Inverse solution of the fetal-circulation model based on ultrasound Doppler measurements

Fetal growth restriction (FGR) is one of the major contributors to adverse perinatal outcome. However, the diagnostic tools currently used for estimating the fetal hemo-dynamic status are still limited. In this study we developed a methodology for estimating fetal hemodynamic parameters. The method is based on a mathematical model of the fetal circulation, an optimization algorithm and measurements of power-Doppler ultrasound. The model estimates parameters of the fetal circulation that are not possible for direct measurement. The method was tested on a cohort of 20 normal and 22 growth-restricted fetuses. In each fetus, power-Doppler velocity waveforms were measured in large number of sites of the fetal circulation. Three-dimensional volume-flow measurements were performed in the placenta to evaluate its resistance to blood flow. Model predictions indicated significant changes in the circulation of FGR fetuses compared to normal fetuses. In the FGR group, the model predicted significant reduction in fetal cardiac output and decreased cardiac output distribution towards the placenta. In FGR fetuses that showed adverse outcome, the model indicated significant increase in cardiac output distribution towards the brain and in the degree of blood shunted by the ductus venosus, indicating severe brain-sparing state in these fetuses. We conclude that patient-specific modeling may be useful in personalizing and optimizing the treatment options in pregnancies complicated by fetal growth-restriction.