Folic acid does not cause diarrhea when taken in early pregnancy and other causes should be considered. Folic acid is an essential nutrient for the human body and is necessary for fetal growth and development. Folic acid is a water-soluble substance that does not usually cause increased intestinal peristalsis or intestinal mucosal secretion, and it does not cause problems with intestinal function, so there is no mechanism associated with diarrhea. When such a condition occurs in a pregnant woman, other causes should be considered for appropriate management. Folic acid in the human body is mainly involved in protein metabolism, combined with vitamin B12 to promote the maturation of red blood cells and hemoglobin synthesis, but also to promote the synthesis of amino acids, nucleic acids and other important macromolecules, so for fetal growth and development is very important, should be supplemented in moderation during pregnancy.