Folic acid is still useful in the second trimester, and should be taken throughout pregnancy, only that it works differently at different stages. Folic acid is an indispensable nutrient for fetal growth and development, and a deficiency of folic acid in pregnant women may lead to low birth weight and heart defects. If folic acid is deficient during the first trimester of pregnancy, it can cause defects in the development of the fetal neural tube, which can lead to malformations. Therefore, women who are preparing for pregnancy can take 0.4mg of folic acid daily starting before pregnancy. If, due to unawareness or other reasons, folic acid was not supplemented in time for preconception and early pregnancy, but is still within the first trimester time frame, it is possible to supplement folic acid in time. In addition, there is no need to worry too much in cases like this because there are many foods rich in folic acid in the usual daily diet. If a pregnant woman does not have a partial diet and pays attention to balanced nutrition, she can take a certain amount of folic acid supplement, but it may not be enough to prevent diseases during pregnancy. In this case, it is enough to pay attention to regular medical checkups at a later stage to exclude fetal dysplasia and malformations.