<P> The parents of the affected individual are typically genetically normal . The extra chromosome occurs by chance . The possibility increases from less than 0.1% in 20 - year - old mothers to 3% in those age 45 . There is no known behavioral activity or environmental factor that changes the possibility . Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing or after birth by direct observation and genetic testing . Since the introduction of screening, pregnancies with the diagnosis are often terminated . Regular screening for health problems common in Down syndrome is recommended throughout the person's life . </P> <P> There is no cure for Down syndrome . Education and proper care have been shown to improve quality of life . Some children with Down syndrome are educated in typical school classes, while others require more specialized education . Some individuals with Down syndrome graduate from high school and a few attend post-secondary education . In adulthood, about 20% in the United States do paid work in some capacity with many requiring a sheltered work environment . Support in financial and legal matters is often needed . Life expectancy is around 50 to 60 years in the developed world with proper health care . </P> <P> Down syndrome is one of the most common chromosome abnormalities in humans . It occurs in about one per 1000 babies born each year . In 2015, Down syndrome was present in 5.4 million individuals and resulted in 27,000 deaths down from 43,000 deaths in 1990 . It is named after John Langdon Down, the British doctor who fully described the syndrome in 1866 . Some aspects of the condition were described earlier by Jean - Étienne Dominique Esquirol in 1838 and Édouard Séguin in 1844 . In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered . </P> <P> Those with Down syndrome nearly always have physical and intellectual disabilities . As adults, their mental abilities are typically similar to those of an 8 - or 9 - year - old . They also typically have poor immune function and generally reach developmental milestones at a later age . They have an increased risk of a number of other health problems, including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders, among others . </P>

Where does the name down syndrome come from