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).
Transverse section through the upper abdomen, which should demonstrate the following fetal landmarks:
AC 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.
The gallbladder may sometimes be seen.
- 1. Bethune, M., Alibrahim, E., Davies, B., & Yong, E. A pictorial guide for the second trimester ultrasound. AJUM August 2013; 16 (3):98-113. Free article.
- 2. AIUM practice guideline for the performance of obstetric ultrasound examinations. J Ultrasound Med. 2013;32 (6): 1083-101. doi:10.7863/ultra.32.6.1083 - Pubmed citation
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Second trimester of pregnancy
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