Ultrasonic measurement of aortic and umbilical blood flow in the human fetus.

The study reports blood velocity and blood flow in the descending aorta and the umbilical vein of 20 normal human fetuses by application of combined B-mode ultrasound and pulsed Doppler technique. All pregnancies and newborns were clinically normal. The echographic examination was performed between 37 and 40 weeks' gestation by an ADR real-time linear scanner 2130 coupled with the Kranzb uhler pulsed Doppler system 8105. The diameter of the vessels was measured by B-mode echogram, and the Doppler beam was directed to form an incident angle between 30 and 65 degrees with the axis of the vessel. The Doppler shift frequency was measured electronically with a spectrum analyzer 8106. Fetal blood velocity waveforms were calculated following the Doppler equation. In the descending aorta, the calculated velocity was 27.7 +/- 6.7 cm/second (mean +/- SD) and the blood flow was 679 +/- 106 ml/minute or 216 ml/kg/minute. In the umbilical vein, the same parameters were 18.3 +/- 4.0 cm/second, 366 +/- 65 ml/minute, and 117 +/- 16 ml/kg/minute, respectively. The average umbilical flow: aortic flow ratio was 0.54 +/- 0.07.