Amniocentesis shows a deletion of chromosome 21 in the region q22.3, meaning a deletion of chromosome 21, which is known as 21-trisomy syndrome. Trisomy 21, also known as Down syndrome, is the most common disorder caused by chromosomal abnormalities.The abnormality of chromosome 21 is due to an abnormality in the division of sperm cells or egg cells during cell division during embryonic development, resulting in the presence of a single chromosome 21 or a deletion of chromosome 21. The mother’s advanced age, genetics, and exposure to teratogens may contribute to the development of the disorder, which is characterized by postnatal intellectual backwardness, peculiar facial features, and growth retardation. If amniocentesis identifies trisomy 21, the pregnant woman and her family should actively communicate with the doctor and negotiate a decision on whether to terminate the pregnancy.