Blood flow velocity waveforms were recorded between the 20th and 40th week of gestation from the umbilical and fetal aorta (n = 230 each) in 130 uncomplicated pregnancies. The S/D ratio, the Resistance Index (RI) and the Pulsatility Index (PI) were calculated. In the umbilical artery the indices showed a significant decrease in the observation interval. In the fetal aorta we could not register any significant change of these indices. All values are presented as reference curves. The importance of the Doppler assessment of the circulation in these vessels for the management of high-risk pregnancy is emphasized.