Pre-pregnancy dental examination is to avoid the occurrence of dental and oral diseases after pregnancy and the adverse effects of medication on the fetus. Because women are prone to dental diseases after pregnancy, it is mainly related to the increase of hormone level in the body and the change of oral environment after pregnancy. In addition, the increase of stomach acid caused by pregnancy vomiting in early pregnancy, as well as the change of oral environment caused by the change of pregnant women’s diet, are prone to gum disease and oral disease. If you cannot maintain good hygiene during pregnancy, swollen and bleeding gums will occur and the pain will be more serious than usual. The increase of stomach acid in early pregnancy vomiting is more likely to produce tooth decay, in addition, dental disease in pregnant women will also cause premature birth, which may be mainly due to bacteria in the gums entering the bloodstream and crossing the placenta to infect the fetus and cause premature birth. Therefore, dental checkups should be conducted before pregnancy, and dental and oral diseases should be treated in time to avoid adverse effects on the fetus with medication after pregnancy.