Ductus venosus flow

In the assessment of ductus venosus flow the gestation should be 11⁺⁰ to 13⁺⁶ weeks and the CRL 45-84 mm.

• The fetus should not be moving.
• The magnification of the image should be such that the fetal thorax and abdomen occupy the whole screen.
• A right ventral mid-sagittal view of the fetal trunk should be obtained.
• Colour flow mapping should be used to demonstrate the umbilical vein, ductus venosus and fetal heart.
• The pulsed Doppler sample should be small (0.5-1.0 mm) to avoid contamination from the adjacent veins and it should be placed in the yellowish aliasing area.
• The insonation angle should be less than 30 degrees.
• The filter should be set at a low frequency (50-70 Hz) to allow visualization of the whole waveform.
• The sweep speed should be high (2-3 cm/s) so that the waveforms are widely spread for better assessment of the a-wave.