The health of the child is the top priority of the family, but sometimes there are embryonic chromosomal abnormalities, and the next is a brief introduction to the causes of embryonic chromosomal abnormalities. 1, genetic factors: if the parents have abnormal chromosomes or carry genes, then the child will most likely also have chromosomal abnormalities, accounting for 25% of birth defects; 2, environmental factors: in the early 3 months of pregnancy is a highly sensitive period leading to fetal abnormalities, if the pregnant woman is affected by the environment, food, drugs, viruses, etc. during this period, for example, home decoration, virus infection, pesticides in food effects, all may increase the risk of chromosomal abnormalities. Only 10% of birth defects; 3, the interaction of genetic and environmental factors and birth defects of unknown cause account for 65%. 4, abnormalities in the formation of sperm and eggs can lead to abnormalities in the development of fertilized eggs, for example, after the advanced age of women over 35 years, when the eggs are formed, chromosome 21 does not split into two eggs, but runs into one egg, which leads to three chromosomes of chromosome 21 when the sperm-egg union occurs, forming an abnormality of 21-trisomy sign. In general, there are many causes that trigger chromosomal abnormalities and when they occur, the couple should have their chromosomes examined; however, it is not easy to find an obvious cause for abnormalities that occur at the time of sperm-egg union.