In transverse fetal ultrasound, spina bifida may show which two shapes described by the letters U and V?

• A. U or V
• B. Circular
• C. Oval
• D. Square

Answer: (A)

In transverse fetal spine imaging, the way the posterior vertebral arches fuse is a key clue. When spina bifida is present, the posterior elements don’t fuse properly, so the spinal canal edge takes on a notch that can look like a U or a V on the cross-sectional view. A U-shaped appearance means the posterior arches form a notch that’s more shallow, while a V-shaped appearance shows a deeper, more pronounced divergence of the arches. These U- and V-shaped configurations are classic landmarks of open neural tube defects in the spine on ultrasound, helping distinguish spina bifida from a normal, closed spine. Shapes like circular, oval, or square don’t describe this particular posterior-element pattern and aren’t typical findings for spina bifida in the transverse view.