What is the maximum normal atrial width of the lateral ventricle on fetal ultrasound?

• A. 8 mm
• B. 10 mm
• C. 12 mm
• D. 15 mm

Answer: (B)

Measuring the atrial width of the fetal lateral ventricle is a quick screen for ventriculomegaly. The upper limit of normal is about 10 mm. In the axial view at the level of the choroid plexus, you place calipers on the inner edges of the ventricle to get this measurement. If the atrial diameter exceeds 10 mm, ventriculomegaly is diagnosed and warrants further evaluation, since dilation can be associated with various CNS issues. So, 10 mm is the maximum normal value. A value like 12 or 15 mm would indicate dilation, while 8 mm is normal but not the upper limit.