MODEL RELEASED. Pregnancy supplement. Pregnant woman taking a tablet containing folic acid. Folic acid, vitamin B9, is an important supplement in pregnancy. It is necessary for the activities of enzymes involved in the manufacture of nucleic acids (the cell's genetic material). It therefore plays an important role in growth, reproduction, nervous system function, and in the production of red blood cells. Folic acid is found in leafy green vegetables, peas and beans, mushrooms, egg yolk and liver. A deficiency of folic acid can lead to anaemia, poor growth in children, and sores around the mouth.