Down Syndrome

(DS; Trisomy 21)


Down syndrome is a disorder of the genes. It can cause birth defects and other medical problems. There are 3 types of Down syndrome:

  • Trisomy 21
  • Mosaic Trisomy 21
  • Translocation Trisomy


Chromosomes hold your DNA. Your DNA hold the plans for how your body grows and functions. There are 23 pairs of chromosomes. Down syndrome is a problem with pair 21. There is extra genetic material on pair 21. Each type of Down syndrome has its own genetic change:

  • Trisomy 21 is caused by:
    • An extra chromosome
    • Occurs when the cell divided in the egg or sperm
  • Mosaic Trisomy 21—extra chromosomes in some cells
    • Translocation trisomy
    • Part of the chromosome breaks off and reattaches to another chromosome
    • Can be inherited from a parent

Risk Factors

Factors that increase the chance for Down syndrome include:

  • Genetics—if a parent is a carrier of Translocation Down syndrome
  • Mother is 35 years and older during pregnancy
  • Sibling with Down syndrome


Infants born with Down syndrome may have some or all of the following physical features:

  • Flat facial features, a somewhat depressed nasal bridge and a small nose
  • Upward slanted eyes, small skin folds on the inner corner of the eyes
  • Short neck with loose skin
  • Misshaped and/or low set ears
  • White spots on the colored part of the eye
  • Single skin crease in the palm of the hand
  • Excess flexibility in joints
  • Sight and hearing problems
  • Large and protruding tongue
  • Excessive space between the large and second toe

Overall health will vary from person to person. Talents, abilities, and pace of development will vary too. People with Down syndrome may be born with or develop:

  • Vision problems
  • Hearing loss
  • Heart defects
  • Acute leukemia
  • Frequent ear infections
  • Instability of the back bones at the top of the neck, which can result in compression injury of the spinal cord
  • Gastrointestinal obstruction
  • Hirschsprung disease
  • Celiac disease
  • Sleep problems, such as blocked airways during sleep, daytime sleepiness, sleep anxiety, and sleep walking
  • Increased incidence of dementia in older adults
  • Urinary system defects
  • High blood pressure in the lungs
  • Seizures
  • An under-active thyroid
  • Slow growth
  • Late to sit, walk, and toilet train
  • Speech problems
  • Obesity
  • Emotional problems

Most of these health problems can be managed. Most with Down syndrome have a life expectancy of about 55 years.


The doctor may suspect Down syndrome at birth. Some features can be very distinct. A blood test will be done to confirm.

Down syndrome may also be found before birth. Prenatal tests may include:

Screening Tests

A screening test is done to find out your risk of having a child with Down syndrome. 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 of pregnancy. An ultrasound may also be done. It may show certain physical signs in the fetus.

A follow-up test may be done later if you have a negative test.

Sometimes a test may be positive even though Down syndrome is not present. Other tests may be done to help confirm the test result.

Diagnostic Tests

More invasive tests can take a tissue sample from the fetus. It will be used to examine genes and confirm Down syndrome. These tests include:

  • Chorionic villus sampling (CVS)—Usually done between 10 and 12 weeks of pregnancy
  • Amniocentesis —Usually done between 12 and 20 weeks of pregnancy
  • Percutaneous umbilical blood sampling (PUBS)—Usually done after 20 weeks of pregnancy

These tests are about 98% to 99% accurate. However, they also create a small risk of miscarriage. Discuss these risks and benefits with your doctor.


Fetus Chromosomes
Copyright © Nucleus Medical Media, Inc.


There is no cure for Down syndrome. However, most people with Down syndrome can be an active part of the community. This includes school, work, and recreation. Some people with Down syndrome live with family. Others live with friends or on their own.

Support care can help with developmental challenges. Medical care may be needed for other complications.

Infants and Children

Infants with Down syndrome may take longer to feed. A child with Down syndrome will also start to talk, walk, and play later than others. Your medical team will help to check milestones for your child. Living at home and support therapy will help a child reach their full potential.

Medical care for related issues, like heart valves, may also be needed. Some may require surgery.


Learning opportunities may be increased with:

  • School programs designed to meet the child's unique needs.
  • Mainstreaming children into regular public school classes. Additional support can be added as needed.

Rehabilitation Services

Therapy needs can vary. Options include:

  • Speech therapy—to help speech development
  • Physical therapy—to assist in walking and overall conditioning
  • Occupational therapy—fine motor activity to help with activities of daily living
  • Counseling—mental health support

Support Services

Look for support services for you child. This may include:

  • Early learning programs for children
  • Transportation and education opportunities for adults
  • Work skill training and employment support
  • Life coaching and life skills training

Support groups can also be helpful for caretaker and person with Down syndrome.


There are no known steps to prevent Down syndrome.


National Down Syndrome Congress
National Down Syndrome Society


Canadian Down Syndrome Society


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Last reviewed March 2018 by EBSCO Medical Review Board Rimas Lukas, MD
Last Updated: 5/7/2014

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