Trisomy 18 is a chromosomal abnormality usually caused by exposure to strong rays, high concentrations of benzene, heavy metals and other harmful substances during the early stages of pregnancy, which can cause chromosomes to not segregate properly during meiosis of the embryo sac, and can also be related to genetic factors and maternal age. The main clinical manifestations of the disease are growth disorders, i.e. mental retardation and skeletal and muscular dysplasia in the child. It is accompanied by multiple deformities, such as long anterior and posterior head diameter, small head circumference, protruding occipital bone, short chest sternum, and small nipples. Genitalia can be seen as perineal anomalies and anal atresia, and the endocrine system can have thyroid, thymus and adrenal gland dysplasia. The survival rate is low, with 50% of children dying within 2 months, less than 10% surviving at age 1, and only 1-2% surviving to age 10. If both Down’s syndrome and non-invasive DNA tests show a high risk and amniocentesis results also show chromosomal abnormalities, the child with trisomy 18 can be basically judged and the pregnancy can be terminated in time to ensure eugenics. Therefore, women of childbearing age should do genetic counseling carefully before pregnancy, and should conduct pregnancy checkups and prenatal diagnosis in a standardized manner during pregnancy, and should pay attention to avoid exposure to chemicals, radiation and other undesirable factors during pregnancy to reduce the risk of the disease.