A structural abnormality of the caudal end of the neural tube, more common in diabetic patients, presents as absent sacrum and fused pelvis or short femurs. This is known as?

• A. Caudal Regression
• B. Anencephaly
• C. Encephalocele
• D. Spina Bifida

Answer: (A)

Caudal Regression Syndrome is a spectrum of malformations of the caudal end of the neural tube. The presentation described—absent sacrum with a fused pelvis or short femurs—fits sacral agenesis, a hallmark of this condition. It is notably more common in infants of diabetic mothers due to disruptions in early embryonic development when blood sugar control is poor.

In ultrasound, you’d expect to see little or no sacral formation, pelvic anomalies such as a fused or abnormal pelvic ring, and limb shortening from the impaired development of the caudal region. This pattern clearly distinguishes it from other neural tube defects: anencephaly involves absence of the brain and skull bones at the cranial end; encephalocele is herniation of brain tissue through a skull defect; and spina bifida refers to defects in the posterior vertebral arches along the spine but does not specifically describe sacral agenesis or pelvis fusion.