Women who are preparing to become pregnant can start taking folic acid 3 months before they become pregnant and take it at least until the end of the third month of pregnancy. Folic acid, also known as vitamin B9, is a water-soluble vitamin that promotes the maturation of megaloblasts in the bone marrow. Deficiency of folic acid can cause megaloblastic anemia as well as leukopenia. In clinical practice, folic acid is mainly used to prevent neural tube abnormalities and cleft lip, in addition to treating macrocytic anemia. Women of childbearing age should take daily folic acid supplements starting 3 months before conception and continuing until the end of the third month after conception. It should be noted that the short-term effect of folic acid is not obvious when a woman is deficient in folic acid, so mothers-to-be need to take folic acid tablets consistently. In addition, taking vitamin c and folic acid at the same time may inhibit the absorption of folic acid in the gastrointestinal tract and should be avoided at the same time as vitamin c.