Within the United States, the cases of the syndrome are not steady, but have increased by 24.2 percent from 1979-1983 to 1999-2003. Down syndrome was first described in 1866 and named after Dr. John Langdon Down, although Jérome Lejeune officially recognized the condition in 1959 as having an additional chromosome.
There are three types of Down syndrome. Trisomy 21 (nondisjunction) accounts for 95 percent of cases, translocation accounts for four percent of cases and mosaicism accounts for one percent.
Facts about Down syndrome:
- Down syndrome is the most commonly occurring chromosomal condition. One in every 691 babies in the United States is born with Down syndrome.
- There are more than 400,000 people living with Down syndrome in the United States.
- Down syndrome occurs in people of all races and economic levels.
- The incidence of births of children with Down syndrome increases with the age of the mother. But due to higher fertility rates in younger women, 80% of children with Down syndrome are born to women under 35 years of age.
- People with Down syndrome have an increased risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer’s disease, childhood leukemia, and thyroid conditions. Many of these conditions are now treatable, so most people with Down syndrome lead healthy lives.
- A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees or not at all.
- Life expectancy for people with Down syndrome has increased dramatically in recent decades – from 25 in 1983 to 60 today.
- People with Down syndrome attend school, work, participate in decisions that affect them, and contribute to society in many wonderful ways.
- All people with Down syndrome experience cognitive delays, but the effect is usually mild to moderate and is not indicative of the many strengths and talents that each individual possesses.
- Latinas continue to have children with Down syndrome due to their age at the time of pregnancy. It was stated before that at the age of 40, probabilities increase to 1 in 100.
- The overall reduction in live births with Down syndrome in 1989–1991 that could be attributed to prenatal diagnosis and elective abortion of affected fetuses was 25.8 percent, with 49.1 percent of it being observed at pregnancies at 35 years.
- In 1990–1991, Latinos showed having the lowest overall reduction which was of 10 percent, while whites had the highest reduction of 46.3 percent.