In most cases, Down syndrome is caused by an extra chromosome 21. Downs children have a widely recognized characteristic appearance. Retardation of normal growth and development is typical and most affected children never reach average adult height. The average mental age achieved is 8 years old. Congenital heart defects are frequently present in these infants.
Early mortality is often a result of cardiac abnormalities.
Obstruction of the gastrointestinal tract may require major surgery shortly after birth. Prevention Down syndrome can be detected in a fetus in the first few months of pregnancy by examination of the chromosomes obtained by amniocentesis . The parents of a child with Down syndrome are at increased risk for having another child with Down syndrome and should be made aware of amniocentesis. Mothers who become pregnant after age 40 are also at increased risk for having a child with Down syndrome. Characteristic abnormalities are revealed by a physical examination .