Achieving Correct Abdominal Section

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It is important to ensure that the measurement is truly transverse and at right angles to the long axis of the fetal spine (axial). Oblique sections through the abdomen will result in measurement errors:

1. Section A is a true axial plane. The umbilical vein lies within the anterior third of the fetal abdomen. Only a short segment is seen because the scan plane is axial to the course of the vein
2. Section B is through the abdomen at the point at which the umbilical vein joins the portal vein within the liver. Although this section can be used to measure the abdomen, it may be difficult to differentiate from section C unless the anatomy is clearly understood
3. Section C shows the oblique plane through the abdomen, following the course of the left portal vein and the ductus venosus. This will produce inaccurate measurement