Down Syndrome

What is Down syndrome?

Down syndrome is a genetic condition. It occurs when a child is born with 47 chromosomes (say KRO-mo-zome) instead of the usual 46. The extra chromosome causes delay in brain development and physical abnormalities. Children can be born with Down syndrome regardless of ethnicity, gender and socio-economic status.

Down syndrome is also known as Trisomy 21.

Signs and symptoms

Down syndrome symptoms vary for every child and range from mild to severe. Children with Down syndrome have common physical features but still look like family members. These features include:

  • upward slanting eyes with clear skin folds at the inner corner of the eyelids
  • small, lowset ears
  • small mouth
  • small, round face with full cheeks
  • large tongue that sticks out
  • single crease in the palm of the hand
  • flattened nose
  • flat back of the head
  • decreased muscle tone at birth
  • floppy limbs
  • extra skin at the nape of the neck
  • short stature
  • abnormal mental and physical development

Causes of Down syndrome

Most children are born with 23 pairs of chromosomes.  In the most common form of Down syndrome, a person has 3 copies of the 21st chromosome, instead of the usual 2. The error occurs very early, when the fetus is developing in the womb.

Down Syndrome Karyotype
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People with Down syndrome have an extra copy of chromosome 21.

The age of the mother’s eggs may have something to do Down syndrome. A third of all babies with Down syndrome are born to women over 37 years old.

Risk factors

The risk of having a baby with Down syndrome increases with the mother’s age. Because of this, women over age 35 are offered special tests during pregnancy to check the baby’s chromosomes.


Many children born with Down syndrome will face health problems as babies, children, and adults. Children born with Down syndrome may have one or more of these medical conditions:

  • heart defect
  • intestinal abnormality
  • eye problems
  • hearing problems
  • recurrent ear infections
  • developmental dysplasia of the hip
  • sleep apnea
  • underactive thyroid gland (hypothyroidism)
  • instability of the neck joints
  • more likely to catch infections

Children with Down syndrome have a greater chance of developing acute leukemia, although this is still rare. Children with Down syndrome are also more likely to be obese. Adults with Down syndrome are more likely to develop Alzheimer’s disease and hardening of the arteries at an early age.

What your doctor can do to help

Screening tests can help to find out if an unborn fetus will be born as a child with Down syndrome. There are several different kinds of tests.

An ultrasound can be done in weeks 10 to 14 of pregnancy. It can help estimate the risk that a fetus has Down syndrome by looking for the physical abnormalities associated with the condition.

Blood tests can also be done between weeks 11 and 16 of the pregnancy.

If these tests show a higher risk of Down syndrome, other test can be done. These include chorionic villus sampling and amniocentesis (say am-nee-oh-sen-TEE-sus), which are the most accurate tests.  It is very important to discuss any test results with your doctor and family.

At birth, all babies are examined for typical features of Down syndrome. If Down syndrome is suspected, a blood test is done.

If a baby has Down syndrome, other tests will be done to find out if there are problems with the heart, intestines, or other parts of the body.

How to help your child with Down syndrome

Get support

The mental and physical effects of Down syndrome create challenges for the baby’s parents and for the child herself as she gets older. Parents usually dream of having a “perfect” baby. Parents may feel disappointed when they realize that their baby has a birth defect. They may go through many emotions, including shock, denial, sadness, and anger.

Seek help from your doctor and community. Parents are not alone. Many support groups exist to help parents and children with Down syndrome. Healthy and happy parents are more helpful to the child.

Find resources

Most parents will have questions or concerns about their child’s growth and development. Your child’s doctor or therapists can provide information on how to help your child reach her potential. Support groups can also offer guidance on working with teachers, introducing your child to peers, and other aspects of growth and development.


There is no specific therapy for children with Down syndrome. Almost all children with Down syndrome will go to school, and may even join regular classrooms. Although extra help is often needed, many schools offer assistance in class. Since children with Down syndrome are a little slower in learning, reading and writing, special help may be needed. For example, speech therapy may strengthen language skills.

Physical or occupational therapy may improve movement skills. Depending on the child’s condition, surgery may be necessary for any intestinal problems or heart defects.

When to seek medical assistance

Children with Down syndrome should see a doctor and have thyroid tests regularly. A doctor or other health care provider may be able to suggest special education or other help that would benefit the child.


Most children with Down syndrome grow up to lead full and happy lives. They are often sociable and outgoing people. Some graduate from high school. Some keep part-time or full-time jobs. Some have romantic relationships and marry. Many adults with Down syndrome live into their 50s and 60s. However, up to 20% of children with Down syndrome will not live to reach 5 years of age.

Key points

  • Children with Down syndrome have characteristic physical features and slow mental development.
  • Complications may include heart defects and eye and ear problems.
  • Children with Down syndrome will need to see a doctor regularly.
  • Many children with Down syndrome grow up to lead full and happy lives.

Sheila Jacobson, MBBCh, FRCPC


Canadian Down Syndrome Society. "Celebrate! About Down Syndrome": Last accessed May 2010.

Canadian Down Syndrome Society. Last accessed May 2010.

National Down Syndrome Society. Last accessed May 2010.

National Geographic Kids, "I have Down Syndrome—Know Me Before You Judge Me" Text by Melissa Riggio as told to Rachel Buchholz. Last accessed May 2010.

NDSS: Down Syndrome Fact Sheet

Stein, Rob. "Down Syndrome Now Detectable In 1st Trimester: Earlier Diagnosis Allows More Time for Decisions", Washington Post, November 10, 2005. Last accessed May 2010.