Doppler ultrasound of the umbilical artery

(Upper panel) Color flow depiction of umbilical blood flow in a normal pregnancy. The cursor line representing the Doppler ultrasound beam path can be seen aligned with the vascular flow axis. The two short horizontal lines indicate the Doppler interrogation site in the umbilical arterial flow.
(Lower panel) Doppler waveforms: the vertical axis shows the scale of the flow velocity. Note the low wall filter (40 Hz) depicted in small print in the upper right area of the image panel. The waveforms show prominent end-diastolic flow reflecting low impedance in the fetoplacental arterial circulation downstream from the measurement point.