[Ultrasound study of blood flow velocity in the umbilical artery].

The blood flow velocity waveforms fo the umbilical artery were examined in 101 healthy pregnant women in 146 occasions. A Kranzbühler 8130 Duplex Doppler equipment was used in all of the examinations. Their results were estimated by the A/B ratios (A = systolic peak, B = end diastole) and the Resistance Indexes (Formula: see text). It was found that the A/B ratio decreased from 3.0 to 2.0 and the Resistance Index from 0.6 to 0.5 from the 28th week of pregnancy till term. The changes showed that the resistance of the placental bed decreased continuously in healthy pregnant woman during the third trimester.