[Examination of the reduction of umbilical circulation in fetuses with variable decelerations of heart rate using Doppler sonography of the umbilical artery].

4 patients with ruptured membranes and spontaneous labour showed variable decelerations of the fetal heart rate. Blood flow velocities of the umbilical arteries were measured by means of pulsed Doppler ultrasound. The flow velocity waveforms, being normal between the contractions, showed a rapid change to absent and reverse diastolic flow during uterine contraction. By means of quantitative estimation the forward flow as as high as the measured reverse flow in the umbilical artery, resulting in a stop of placental perfusion. Computer-added reconstruction of the curve of fetal heart frequency revealed the exact temporal relation between reduction of umbilical artery perfusion and deceleration of fetal heart rate as well as the relation between recovery of the fetal heart rate and normalisation of blood flow in the umbilical artery. Using this noninvasive method, we could analyze for the first time the acute changes of umbilical artery perfusion in relation to changes of the fetal heart rate in human fetus. A stop in placental perfusion does not always mean an absence of any movement of the fetal blood column. We could demonstrate that this is due to a systolic forward and diastolic reverse flow in the same extent. The described acute flow alterations are discussed as a model for flow alterations described in high risk pregnancies with abnormal fetoplacental perfusion.