![]() Ultrasound machines with the appropriate probe and capability simultaneously display two images: a B-scan image to locate the vessel needs to be examined and the other displays the Doppler beam to interrogate the site needed to study blood flow. The use of Doppler during antenatal fetal surveillance has involved assessment of (1) the umbilical arterial and venous flow velocity waveforms, (2) the fetal cerebral circulation, and (3) the fetal venous circulation, in particular the ductus venosus. Placental insufficiency is the primary cause of intrauterine growth restriction in normally formed fetuses and can be identified using umbilical artery Doppler velocimetry. There is a strong association between reduced end-diastolic umbilical artery blood flow velocity and increased vascular resistance in the umbilical placental microcirculation.Īlso, abnormal umbilical artery Doppler waveforms have been associated with an increased risk of fetal acidosis, as measured during cordocentesis, and may improve the performance of the biophysical profile score in predicting fetal acidemia and hypercarbia. Umbilical artery Doppler waveforms provide an estimate of downstream placental vascular resistance and placental blood flow. Each wave basically has systolic and diastolic components. This depends on few points: vessel length, caliber, wall elasticity and distance from the cardiac pump. In the human body each vessel has its own specific waveform. The same applies to a train when it is coming to the station and when it is leaving it. Many examples were later described : the change in sound of the ambulance when it is coming near OR away from the listener. This phenomenon was properly explained as change of frequency when there is a change of velocity, later known as the Doppler effect or the Doppler shift. The colour or brightness becomes more apparent if the star is coming towards earth, or, it fades away if the star is going away from earth. He described the apparent changes in colour of light (intensity) emitted by stars when they come near or far from earth. The Doppler phenomenon or Doppler effect was first described by Christian Johanan Doppler (1803- 1853).
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