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Down Syndrome

(DS; Trisomy 21)

Definition

Down syndrome is a common genetic disorder. Down syndrome causes birth defects, medical problems, and some degree of intellectual disability.

Causes

Chromosomes contain the genetic makeup of your body. They occur in 23 pairs within the body. Down syndrome is a problem with chromosome pair 21. There is extra genetic material on the chromosome that may be caused by:

Risk Factors

Factors that increase the chance for Down syndrome include:

Symptoms

Infants born with Down syndrome may have some or all of the following physical features:
The degree of medical problems and intellectual disability is different for each person. Talents, abilities, and pace of development will be different, too. People with Down syndrome may be born with or develop:
Most of these health problems are treatable. The majority of people born with Down syndrome have a life expectancy of about 55 years.

Diagnosis

Doctors can usually identify a child born with Down syndrome at birth. When Down syndrome is suspected, a blood test will be done to confirm it.
Down syndrome may also be diagnosed before birth. There are screening tests and diagnostic tests to help identify chormosome abnormalities before birth.

Screening Tests

A screening test is done to estimate the risk of having a child with Down syndrome. Your doctor will use the results of a variety of blood tests and the mother's age to estimate the risk. Blood tests may include:
  • Triple screen—Alpha-fetoprotein Plus
  • Quadruple screen
  • Cell-Free Fetal DNA Testing
Screening may be done as early as 11 weeks. It may also include both ultrasound imaging and blood screening. There should be a follow-up in the second trimester for those who have a negative screening.
A small amount of women who have screening will be given false-positive readings. This means the test indicates Down syndrome even when it does not exist.

Diagnostic Tests

Diagnostic tests will tell if the fetus actually has Down syndrome. These tests include:
  • Chorionic villus sampling (CVS)—Usually done between 10 and 12 weeks
  • Amniocentesis —Usually done between 12 and 20 weeks of gestation
  • Percutaneous umbilical blood sampling (PUBS)—Usually done after 20 weeks
These tests are about 98%-99% accurate. Each test requires that a small piece of tissue be removed from the placenta or umbilical cord. This creates a small risk of miscarriage with these tests.
Amniocentesis
Fetus Chromosomes
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Treatment

There is no cure for Down syndrome.
Some newborns may need surgery to repair serious medical problems, like heart defects.
Treatment may be needed for severe problems or to help with developmental delays. Living at home and receiving special therapy helps children with Down syndrome achieve their full potential. Most people with the condition can actively participate in the community. This includes activities at schools, jobs, and various leisure activities. Some people with Down syndrome live with family, some live with friends, and some live independently.

Baby Care

Infants with Down syndrome may take longer to feed. A child with Down syndrome will also start talking, playing, and performing other activities later than normal.

Education

Learning opportunities may be increased with:
  • School programs designed to meet the child's special needs.
  • Mainstreaming children into regular public school classes with additional support as needed

Rehabilitation Services

Speech, physical, and occupational therapy may improve abilities. Therapy can help with speech, walking, and performing activities of daily living.

Social Services

Professional support helps a family cope with caring for a child with birth defects and intellectual disability. Mental health professionals offer help with managing emotional problems.

Prevention

There are no guidelines for preventing Down syndrome. If you have concerns about having a child with Down syndrome, consider getting genetic counseling before becoming pregnant.

RESOURCES

National Down Syndrome Congress http://www.ndsccenter.org

National Down Syndrome Society http://www.ndss.org

CANADIAN RESOURCES

Canadian Down Syndrome Society http://www.cdss.ca

Health Canada http://www.hc-sc.gc.ca

References

Benn P, et al. Prenatal detection of Down syndrome using massively parallel sequencing (MPS): A rapid response statement from a committee on behalf of the Board of the International Society for Prenatal Diagnosis, 24 October 2011. Prenat Diagn. 2012;32:1-2.

Committee opinion No. 545: Noninvasive prenatal testing for fetal aneuploidy. Obstet Gynecol. 2012;120(6):1532-1534.

Down syndrome. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated November 2, 2012. Accessed May 21, 2013.

Down Syndrome. National Institute of Child Health and Human Development website. Available at: http://www.nichd.nih.gov/health/topics/down/Pages/default.aspx. Updated April 3, 2013. Accessed May 21, 2013.

Malone FD, Canick JA, et al. First- and second-trimester evaluation of risk (FASTER) research consortium. First-trimester or second-trimester screening, or both, for Down's syndrome. N Engl J Med. 2005;353:2001-2011.

What is Down syndrome? National Down Syndrome Society website. Available at: http://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome. Accessed May 21, 2013.

3/12/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Carter M, McCaughey E, et al. Sleep problems in a Down syndrome population. Arch Dis Child. 2009;94(4):308-310.

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