Under normal circumstances, it is recommended that women start taking oral folic acid 3 months before pregnancy until 3 months after pregnancy. Folic acid belongs to B vitamin derivatives, and the main purpose of folic acid supplementation is to prevent the occurrence of fetal neural tube defective diseases, such as anencephaly, fetal spina bifida or congenital neural tube malformation, etc. It also has a certain preventive effect on fetal congenital heart disease. It is generally recommended that women start supplementing folic acid 3 months before preparing for pregnancy until 3 months after pregnancy, and according to the recommendations in the Dietary Guidelines for Chinese Residents 2016, 400mg of folic acid should be taken orally every day. However, for women who have a history of neural tube defects in the fetus, it is necessary to strictly follow the doctor’s instructions to appropriately increase the dosage or extend the duration of time to take, and even some women taking folic acid will continue throughout the pregnancy. Therefore, women who take folic acid supplements for a long period of time should do so under the guidance of an obstetrician/gynecologist or nutritionist.