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Facts about Down Syndrome

Down Syndrome Facts


Updated May 23, 2014

Need some quick facts about Down Syndrome? The list below covers some of the major points about Down syndrome and is a good way to get a quick start learning about Down syndrome.

Down Syndrome

One in every 733 babies is born with Down syndrome.

Each year, 6000 babies are born with Down syndrome in the United States.

There are 350,000 people with Down syndrome in the United States.

There are over 4 million people in the world with Down syndrome.

Down syndrome occurs equally in all ethnic, racial, religious and socioeconomic groups.


Trisomy 21 is the most common chromosome abnormality seen in liveborn children.

Full trisomy 21 accounts for 95% of cases of Down syndrome.

Mosaic Down syndrome accounts for 2-3% of cases of Down syndrome.

Translocation Down syndrome accounts for about 2–3% of cases of Down syndrome. Approximately 75% of the unbalanced translocations are de novo (happen for the first time in the person with Down syndrome). The other 25% of translocations are inherited from a parent.

In trisomy 21, the extra chromosome comes from the mother 88% of the time, and from the father 12% of the time.

    The chance to have a child with Down syndrome increases as a mother gets older. With a:
  • maternal age of 35 years, the risk is 1 in 385.
  • maternal age of 40 years, the risk is 1 in 106.
  • maternal age of 45 years, the risk is 1 in 30.

Eighty to eighty-five percent of children with Down syndrome are born to women under 35.

Life Expectancy

Approximately 25% of conceptions with trisomy 21 ends in miscarriage or stillbirth.

Approximately 85% of infants with Down syndrome survive to 1 year of age.

The average life expectancy of a person with Down syndrome, in 1990, was 30 years of age.

Currently, the average life expectancy is 50 years of age.


Center for Disease Control (6 January 2006)."Improved National Prevalence Estimates for 18 Selected Major Birth Defects, United States, 1999–2001."Morbidity and Mortality Weekly Report 54 (51 & 52): 1301–1305.

Huether, C.A. (1998). Maternal age specific risk rate estimates for Down syndrome among live births in whites and other races from Ohio and metropolitan Atlanta, 1970-1989. J Med Genet 35(6): 482–490.

Stray-Gunderson,Karen. Babies with Down Syndrome: A New Parents' Guide Woodbine House. 1995

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