Down syndrome is a syndrome that causes slowed growth, abnormal facial features, and mental retardation. It is caused by an extra chromosome 21. Incidence of Down syndrome is estimated at 1 per 800 births, making it the most common chromosomal abnormality. The maternal age effect influences the risk of conceiving a baby with the syndrome. At age 20 to 24, it is 1/1490, while at age 40 it is 1/106, and at age 49 is 1/11.Genetic counseling and genetic testing such as amniocentesis are usually offered to families who may be at increased risk of having a child with Down syndrome. Many children with Down syndrome are born to women under the age of 35 because routine testing is not usually offered to such women. Women over 35 are often given an amniocentesis and 9 out of 10 choose to abort the affected fetus.
The term 'Down's syndrome' was first used in 1961 by the editor of The Lancet 2. It was originally called mongolism or mongolian idiocy, after a perceived resemblance observed by Down between the faces of some of his patients with Down syndrome and the Mongoloid race. This usage is now viewed by medical professionals as offensive and medically meaningless, and is not commonly used today.
While most children with Down syndrome have a lower than average cognitive function, some have earned college degrees with accommodations, and nearly all will learn to read, write and do simple math. The clinical features of Down syndrome include any of a number of features that also appear in people with a standard set of chromosomes. They include a "simian crease" - a single crease across one or both palms, almond shaped eyes, shorter limbs, heart and/or gastroesophageal defects, speech impairment, and perhaps a higher than average risk of incidence of Hirschsprung's disease. Young children with Down syndrome are also more prone to recurrent ear infections and obstructive sleep apnea.
Early educational intervention, screening for common problems such as thyroid functioning, medical treatment where indicated, a conducive family environment, vocational training, etc., can improve the overall development of children with Down syndrome. On the one hand, Down syndrome shows that some genetic limitations can not be overcome; on the other, it shows that education can produce excellent progress whatever the starting point. The commitment of parents, teachers and therapists, to individual children, has produced previously unexpected positive results.