Doppler flow velocity to measure the redistribution of fetal cardiac output in fetal stress.

The pathophysiologic continuum of poor uterine and placental blood flow associated with fetal growth restriction has to be considered the major cause of poor birth outcomes. The main attention in this context is drawn to the possibilities of an early diagnosis of imminent fetal compromise prior to and under delivery. With regard to this, the detection of a reduced fetal oxygen saturation (fetal stress) plays a crucial role, whereas an acute incident causing fetal hypoxemia has to be differentiated from a chronic hypoxemic condition. An acute hypoxemia under delivery is best detected by cardiotocography. Due to its infrequent and unpredictable occurrence, an acute antenatal hypoxemia usually escapes common surveillance methods. Fetal biometry and pulsed Doppler sonography are to be considered the most suitable methods to diagnose chronic hypoxemic fetal conditions. The interrogation of a combination of peripheral and central vessels allow the sonologist to characterize the extend of a progressively deteriorating oxygen supply. However, this correlation is not yet completely understood. Therefore, clinical consequences still have to be drawn by cardiotocographic findings indicating a global cardiac decompensation.