How to Calculate the AC
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Example
Let's take the example of this image.
The anterio-posterior (AP) diameter of the abdomen is 4.0 cm, and the transverse diameter is 4.4 cm.
Remember that the circumference is calculated by multiplying the average diameter by π.
The steps in the calculation are as follows:
- The average diameter is (4.0 + 4.4) / 2 = 4.2
- We can use the value 3.14 for π
- 4.2 (average diameter) x 3.14 (π) = 13.19
Therefore, the abdominal circumference is 13.19 cm.
This measurement is simpler than trying to trace round the circumference and it is reproducible.
Measurement of the abdomen uses end points on the skin surface. This is slightly different from the measurement of the BPD where the measurement is made from the outside of the skull to the inside of the skull.
