The incidence of chromosomal abnormalities associated with the age of the pregnant woman at the time of delivery can be seen clinically, and these ratios refer to the incidence of fetal diseases in the population of pregnant women of the corresponding age. This means that the incidence of fetal chromosomal abnormalities is 0.4% when the expected age of delivery is 35 years old; if the pregnant woman is 40 years old, it rises to 1.4%; and the incidence of fetal chromosomal abnormalities in the general population of non-advanced age (less than 35 years old) is 1:800 on average. therefore, the Measures for the Implementation of the Maternal and Child Health Law of the People’s Republic of China stipulates that “if the age of the first-time mother over 35 years of age, physicians shall conduct prenatal diagnosis for them”. Therefore, doctors are obliged to recommend prenatal diagnosis for older pregnant women. The most common chromosomal abnormality is Down syndrome, also known as “trisomy 21”, which is a congenital chromosomal abnormality. In normal people, there are 46 chromosomes, but in Down’s syndrome, there is an extra chromosome 21, called “trisomy 21”. Patients with Down syndrome have a characteristic facial appearance and may have a combination of heart malformations or other organ developmental abnormalities, often manifesting as mental retardation and poor living skills. There is no treatment available for this condition. Other chromosomal abnormalities include trisomy 18, trisomy 13, and sex chromosomes. The birth of a chromosomal abnormality can be a huge blow and a heavy burden for the pregnant woman, her family and society.