Prenatal support supplements help pregnant women and those hoping to conceive fill any gaps in nutrition. During pregnancy, a woman needs more folic acid and iron than usual. Folic acid helps prevent neural tube defects in babies. These defects are serious abnormalities of the fetal brain and spinal cord. Ideally, you'll begin taking extra folic acid at least three months before you become pregnant. Iron supports the development of the placenta and fetus. Iron helps your body make blood to supply oxygen to the fetus. Iron also helps prevent anemia, a condition in which blood has a low number of healthy red blood cells.