Down’s babies, or Down’s syndrome, are mainly due to genetic problems, and their risk factors include the mother’s advanced age and exposure to teratogenic factors during pregnancy. Down syndrome is caused by an abnormal change in the number or structure of chromosome 21 during fertilization. 1. Advanced maternal age: The aging of eggs in advanced maternal age (usually ≥35 years of age) significantly increases the chance of chromosome 21 nondisjunction during meiosis. And the older the age, the higher the incidence of the baby born. 2. Mother’s exposure to teratogenic factors during pregnancy: environmental teratogenic substances such as pesticides, benzene, radiation exposure, viral infections such as hepatitis B virus infection, certain teratogenic drugs such as sulfonamide antibiotics, etc., can lead to chromosomal aberrations, resulting in babies more likely to suffer from this disease.