Down syndrome is the most common chromosomal disorder, affecting one in every 800 live births. Individuals with Down syndrome are born with three copies of chromosome 21 (another name for Down syndrome is trisomy 21) giving them 47 chromosomes instead of the usual 46.
Individuals with Down syndrome have decreased mental abilities and health problems, including hearing deficits, heart problems, intestinal abnormalities, eye problems, low levels of thyroid hormone, skeletal problems such as joint instability, and poor weight gain in infants. They also develop leukemia more often than those without Down syndrome and have increased risk of infection, problems with the immune system, skin disorders, and seizures. Many Down syndrome babies are suspected of having the condition shortly after birth based on certain physical characteristics. These characteristics can vary greatly between individuals, but generally include:
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Low muscle tone (muscle hyptonia)
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Flat facial profile with a slightly depressed nasal bridge and small nose
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An upward slant to the eyes (oblique palpebral fissures)
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Abnormal ear shape (dysplastic ear)
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A single deep crease across the center of the palm
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Hyperflexibility
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The fifth finger has one flexion furrow instead of two (dysplastic middle phalanx of the fifth finger)
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Small skin folds on the inner corner of the eyes (epicanthal folds)
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Excessive space between large and second toe
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Large tongue relative to overall mouth size
Diagnosis of Down syndrome is usually confirmed by a blood test which looks for the extra chromosome. The condition may also be diagnosed during pregnancy using amniocentesis, CVS (chorionic villus sampling), or Percutaneous Umbilical Blood Sampling (PUBS).
There is no way to prevent Down syndrome. The chance of having a child with Down syndrome increases with the mother’s age, and some researchers suggest that the father’s age may also increase the risk. As a woman (and her eggs) age, there is a greater chance that the chromosomes contained in a fertilized egg may divide improperly. At age 35, a woman’s risk of having a baby with Down syndrome is 1 in 385. At age 40, the risk is 1 in 106; and by age 45, the risk is 1 in 30. However, most children with Down syndrome are actually born to women under age 35 because they have many more babies. Parents who already have a child with Down syndrome are more likely to have another child with the condition.
There is no cure for Down syndrome. However, physical therapy, special education programs, and medical procedures can address some of the problems associated with the condition and can significantly improve the individual’s quality of life, developmental possibilities, and life expectancy. The majority of Down syndrome individuals born today will live past 55 years old and many can achieve semi-independent lives.
If your baby has been diagnosed with Down syndrome, your can find research updates, parent resources, and community support from the National Down Syndrome Society.