Fetal abdominal circumference

Last revised by Patrick O'Shea on 17 Dec 2022

Abdominal circumference (AC) is one of the basic biometric parameters used to assess fetal size. AC together with biparietal diameter, head circumference, and femur length are computed to produce an estimate of fetal weight. In the second trimester, this may be extrapolated to an estimate of gestational age and an estimated date of delivery (EDD).

Sonographic technique

Transverse section through the upper abdomen, which should demonstrate the following fetal landmarks:

Abdominal circumference measurement should not be taken on a foreshortened abdomen and the calipers should be on the skin surface (skin surface should be visible). 

The kidneys and cord insertion should not be visible. The umbilical vein should not be seen up to the skin line, considering a true transverse view (portal sinus, fetal stomach, symmetrical fetal ribs, and the level of the junction of umbilical vein) without maternal abdominal compression.  

The gallbladder may sometimes be seen.

Related pathology

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Cases and figures

  • Figure 1
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  • Case 1: abdominal circumference
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  • Case 2: normal second trimester scan
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