Understanding Down Syndrome

Each year, approximately one in every 800 to 1,000 babies is born with Down syndrome, a condition that may delay a child's physical and mental development.

Down syndrome is a chromosomal disorder that occurs when an extra chromosome — chromosome 21 — is present in either the sperm or the egg at conception. There is no standard profile of a person with Down syndrome. Most people with Down syndrome have mild to moderate mental impairments and are able to live productive and satisfying lives in their communities.

In the past, children with Down syndrome were often placed in institutions because it was believed they would never be able to participate in society. But, today children with Down syndrome can grow up to be productive, independent members of their communities, thanks to the care and support of informed parents and professionals.


Down syndrome is not caused by any action of the child's mother or father, during or before pregnancy, but the chances of having a baby with Down syndrome increase significantly with maternal age or if one parent is a translocated cell carrier.

There are three types of Down syndrome:

  • Trisomy 21 or Nondisjunction: an extra 21st chromosome is replicated in every cell in the body. This faulty cell division is the cause of 95 percent of all Down syndrome cases.
  • Translocation: part of the 21st chromosome breaks off during cell division and attaches itself to another chromosome. This happens during or immediately after conception, and accounts for only three to four percent of Down syndrome cases. In about one-third of translocation cases, one parent is a translocated chromosome carrier.
  • Mosaicism: a very rare form of Down syndrome, accounting for only one to two percent of all cases. Nondisjunction of the 21st chromosome takes place in one of the initial cell divisions after fertilization. This creates a mixture of two types of cells, some with 46 chromosomes and some with 47.

Characteristics of Down Syndrome

  • Low muscle tone
  • Eyes that appear to slant upwards
  • A flat nose bridge and small nose
  • Abnormally shaped ears
  • A horizontal crease on either palm
  • An excessive ability to extend joints
  • Small skin folds on the inner corner of the eyes
  • Excessive space between large and second toe
  • A delay in mastering basic living skills such as rolling over, crawling or responding to others


Early detection is important - it allows intervention services such as physical, occupational and speech therapies to begin at the youngest possible age. Family support and participation are crucial to the success of early intervention.

More than 40 percent of people with Down syndrome are born with congenital malformations of the heart that vary from controllable to life-threatening. Because surgery and other treatments are available, it is important that a baby with Down syndrome be examined by a pediatric cardiologist. Also, because children with Down syndrome often have vision and hearing problems they should be evaluated by hearing and vision specialists between 6 and 12 months of age or earlier if problems are evident.

Early intervention programs aid in the development of children with Down syndrome, and can be found in most communities. Children with Down syndrome also benefit from integrating with other children through day care and nursery school classes, swimming and dance lessons, library activities and other community programs. Parents can turn to professionals, parent support groups, national associations and various publications for guidance in raising a child with Down syndrome.

Watch one family share the impact Easterseals has had on their son with Down syndrome

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