The causes of fetal malformation are complicated, there are mainly three categories: 1, genetic factors: chromosome number or structure abnormalities can lead to fetal malformation, but chromosome abnormalities lead to malformation only 40%-50% of the incidence of fetal malformation; 2, environmental factors: including infection, drugs, chemical substances, drugs, ionizing radiation, etc., all have different degrees of teratogenic effect, environmental factors teratogenic and teratogenic dose Environmental factors are related to teratogenic dose, effect and individual sensitivity, absorption, metabolism and degree of exposure; 3, combined factors: that is, environmental factors and genetic factors work together, mostly polygenic genetic diseases, such as congenital heart disease, neural tube defects, cleft lip, cleft palate and pyloric obstruction and other fetal malformations. In a broad sense, normal chromosomes usually refer to karyotype analysis of G bands between 320-400 bands without abnormalities, and chromosomal microdeletions and microduplications, which cannot be detected by ordinary bands, and microdeletions and microduplications of chromosomes can also lead to fetuses with various malformations in combination. Therefore, the majority of fetal chromosomal abnormalities are combined with malformations of internal organs, skin and limbs, but not all malformed children are necessarily caused by chromosomal abnormalities, but may also be due to environmental factors.