The most dangerous stage of fetal malformation is within 12 weeks of pregnancy, especially between 3 and 8 weeks of pregnancy, during which fetal malformation can be caused by viral infection, exposure to radiation, adverse oral medication, and adverse emotional stimulation. The best time for cell division from fertilized egg cells to fetus is within 12 weeks, and it can develop into arms, legs and eyes during this stage, but this process is especially prone to malformation, and the most serious time is between 3-8 weeks, when the heart and eyes are prone to various malformations, including cleft lip and palate, spina bifida and anencephaly, if stimulated by external sources. However, after 12 weeks, when the fetus has fully grown into a normal human shape, the susceptibility of teratogenicity can be reduced. In the first 3 months of pregnancy, pregnant women need to eliminate all drugs, cosmetics, chemical substances, radiation, noise and other adverse influencing factors, and try to avoid contact with animals such as dogs and cats. In addition, pregnant women need to take folic acid tablets for 3 months at the beginning of pregnancy to prevent fetal neural tube malformation.