Pregnant Women Should Eat Foods High in Folic Acid,such as Beans

Pregnant women should eat foods high in folic acid,such as beans or spinach,during pregnancy.What is the purpose of this dietary recommendation?

A) To help moderate the effects of teratogens to which the fetus might be exposed
B) To reduce the effects of stress on the fetus
C) To ensure sufficient weight gain for a healthy baby
D) To reduce the risk of neural tube defects such as spina bifida