Neural Tube Defects

A 28-year-old primigravida from rural Maharashtra presents for antenatal counseling at 12 weeks of gestation. She has not taken any folic acid supplementation. On detailed history, her mother had a child with spina bifida 15 years ago. Maternal serum alpha-fetoprotein (AFP) is elevated at 2.8 MoM (multiples of median) at 16 weeks. Ultrasound shows a fluid-filled sac protruding from the lumbosacral region with exposed neural tissue. What is the most likely diagnosis?

A 3-day-old male infant born to a 22-year-old mother is referred to pediatrics with a midline lumbosacral mass noted at birth. The mass is covered with skin and hair, and there is no visible CSF leakage. Neurological examination reveals normal lower limb motor and sensory function, and anal tone is intact. Ultrasound of the spine shows a subcutaneous mass with fatty infiltration and a small defect in the underlying vertebral laminae, but no communication with the spinal cord. What is the most likely diagnosis?

Which vitamin deficiency is the primary preventable cause of neural tube defects?