During the first 3 months of pregnancy the gestational sac is in an important growth phase, when the fetus is not yet intact and all organs are still in the developmental stage. Therefore, the most dangerous period for fetal teratogenesis is generally considered to be within 12 weeks of pregnancy. During the first 3 months of pregnancy, the embryo’s metabolism and excretion of toxic substances are not perfect. If stimulated by external drugs, chemicals, radiation or certain viral infections, cell differentiation may be affected, and various malformations, including cleft lip and palate, spina bifida and anencephaly, may occur. In addition, after the 12th week of pregnancy, the fetal organs and systems have differentiated and formed, and the fetus is generally not particularly sensitive to teratogenic substances during this period, but care should still be taken to avoid exposure to adverse environments. It is recommended to take appropriate diet during pregnancy, take folic acid tablets at the beginning of pregnancy under the guidance of professional doctors, avoid straining and emotional excitement, and have regular maternity checkups.