The atrium of the lateral ventricle is measured at what typical size during pregnancy?

• A. 6-10 mm
• B. 1-3 mm
• C. 12-15 mm
• D. 20-25 mm

Answer: (A)

Measuring the atrium of the lateral ventricle is a standard way to assess fetal brain size and screen for ventriculomegaly. This width is taken on an axial view at the level where the ventricle forms the atrium, and it reflects the ventricular CSF space. In a normal fetus during pregnancy, the atrial width is typically around 6 to 10 millimeters. Keeping within this range suggests normal ventricular size; values exceeding about 10 millimeters raise concern for ventriculomegaly or hydrocephalus, while much smaller measurements are not typical and can indicate measurement limitations or fetal positioning. Therefore, 6–10 mm is the typical size during pregnancy.