Trisomy 18 is a chromosomal abnormality, usually caused by exposure to strong rays, high concentrations of benzene, heavy metals and other harmful substances during early pregnancy, resulting in abnormal chromosome segregation during meiosis of the embryo sac. It may also be related to genetic factors, maternal age and other aspects, and the incidence of the disease increases in babies born to mothers who are too young or too old. The main clinical manifestations are growth disorders, i.e., the child is mentally retarded and has poor skeletal and muscular development. There are multiple malformations, such as long anterior and posterior head diameter, small head circumference, prominent occipital bone, short thoracic sternum, and small nipples. Genitals can be seen in perineal abnormalities, anal atresia, and the endocrine system can have thyroid, thymus, and adrenal dysplasia. The survival rate is low, with 50% of children dying within 2 months, less than 10% surviving to age 1, and only 1-2% surviving to age 10. Currently, Down’s syndrome, non-invasive DNA testing and amniocentesis can be used to determine the risk of trisomy 18 in early pregnancy. If Down’s screening and non-invasive DNA show high risk, and amniocentesis also shows chromosomal abnormality, it can be basically judged as a child with trisomy 18, and in order to ensure the eugenics of pregnancy, pregnancy can be terminated in a timely manner. Therefore, women of childbearing age should carefully do genetic counseling before pregnancy, should standardize pregnancy examination and prenatal diagnosis during pregnancy, and should pay attention to avoiding exposure to chemicals, radiation and other undesirable factors during pregnancy, in order to reduce the risk of the disease.