The abdominal circumference measurement is taken along the outer margin of the abdominal skin line at the level of which structures?

• A. Gastric bubble and intrahepatic portion of the umbilical vein at the bifurcation of the portal veins
• B. Head circumference
• C. Femur length
• D. Umbilical artery

Answer: (A)

Abdominal circumference is measured in a true transverse plane of the fetal abdomen, using landmarks that confirm you’re looking through the abdomen rather than the head or limbs. The stomach bubble and the intrahepatic portion of the umbilical vein as it approaches the portal venous bifurcation define that exact cross-sectional view. Placing the calipers on the outer skin margins in this plane gives a consistent, true measure of the abdominal size that can be compared to growth standards.

Measuring at the level of the head (head circumference) or at the femur length would not capture the abdominal cross-section, and using a landmark like the umbilical artery would not reflect the abdomen’s true outer boundary.