What is folic acid? Folic acid, a water-soluble B vitamin, is an important nutrient that has great benefits for human health. Folic acid helps the body make new cells, especially red blood cells. At the same time, it can also improve immunity, prevent cancer, heart disease, stroke, etc. When a woman is pregnant, the importance of folic acid becomes even more apparent. Pregnant women need to supplement folic acid during pregnancy. Pregnant women need to supplement 400-800 micrograms of folic acid every day to reduce pregnancy.