A female neonate is noted at birth to have a gross deformity of her lower back. Examination of the subcutaneous lesion reveals disorganized neural tissue with entrapment of nerve roots. The parents of the neonate ask about the risks for similar birth defects in their future offspring. You mention that supplementation of the maternal diet can reduce the incidence of neural tube defects. What is this important dietary supplement?

Maternal folic acid deficiency has been associated with an increased incidence of neural tube defects, and folic acid has, therefore, been approved for inclusion as a food supplement in commercial flour. Deficiencies of vitamins in the other choices are not associated with congenital dysraphic anomalies. Niacin deficiency results in pellagra. Thiamine deficiency (choice C) causes Wernicke syndrome and beriberi. Vitamin B12 deficiency (choice E) leads to pernicious anemia.Diagnosis: Neural tube defect