The main effects of folic acid deficiency in pregnant women on the fetus are as follows: 1. It increases the chance of neural tube abnormality in the fetus, especially in the first 3 months of pregnancy, and the chance of such abnormality in the fetus will be higher if folic acid is deficient. The patient needs to do NT screening or amniotic fluid puncture to determine whether the fetus has this malformation.2. Folic acid deficiency in pregnant women can cause anemia in pregnant women, and if the pregnant woman is anemic, it will affect the fetus and cause lack of nutrition and lack of oxygen in the uterus, which will lead to growth restriction of the fetus, in addition to frequent fetal movement when the fetus is anoxic, and the umbilical cord is prone to bypass or knotted umbilical cord In addition, the fetus may be prone to frequent fetal movements, cord winding or cord knotting, and stillbirth in the middle and late stages of pregnancy. Therefore, when a pregnant woman is tested for folic acid deficiency, she must choose folic acid supplementation according to her condition.