[Evaluation of the central hemodynamics of the fetus using pulsed Doppler ultrasound].

Using pulsed Doppler, blood flow in the cerebral arteries was measured to assess the fetal central circulation. The Pulsatility-Index (PI) was calculated as a qualitative parameter of flow velocity waveforms. In 418 normal singleton pregnancies we performed 558 measurements between the 27th and 40th week of gestation to get normal range values of the PI. The curve shows a small decrease in the observed interval. In cases of an intrauterine hypoxia the resistance of the central vessels decrease to render the distribution of the fetal blood volume. The result of this is a centralisation of the fetal circulation. 131 high risk pregnancies were investigated and in 21 cases such a centralisation was registered. The fetal outcome of these fetuses was significantly worse compared with fetuses having a normal central flow resistance. We found for example a higher rate of caesarean sections because of fetal distress when the Pulsatility-Index was below the 5th percentile. The sensitivity of the method in prediction caesarean section for fetal distress was 59.3%, the specifity 95.3%.