[Fetal umbilical arterial blood flow velocity waveforms as measured in the uterus by pulsed Doppler and B-mode ultrasound].

3.0 MHz Doppler ultrasound was used to measure the umbilical arterial blood flow velocity waveforms (FVW) in 174 fetuses between 22-42 weeks of gestation. The A/B ratio (systolic/diastolic), resistance index (RI), pulsatility index (PI) and impedance index (ImI) were used as indexes of placental flow resistance. In normal pregnancy (n = 152), 460 measurements were performed. Analysis of these waveforms demonstrated that the placental is an organ of low vascular resistance and that placental resistance to blood flow gradually declines with advancing gestational age. Our results indicated a significant negative correlation between each of the four indexes and gestational age. There was a small but significant decrease in all four indexes, from 22-42 weeks. 56 scans were performed on 22 fetuses with intrauterine growth retardation (IUGR). The sonograms from these IUGR fetuses showed different characteristics which implied a high distal impedance to the blood flow. 16 of these (72.7%) presented an abnormal increase in all four indexes.