Down syndrome is a chromosomal disorder. Instead of having 46 chromosomes, 23 from each parent, a child with Down syndrome ends up with 47 chromosomes. This leads to delays in development and other health problems. The life expectancy for Down syndrome patients varies by country, ranging from 30 to 50 years.
Function
The cause of Down syndrome is a random error that occurs during the development of the egg, sperm or embryo. Researchers have not identified any environmental and behavioral risk that increases the probability of having a child with Down syndrome. The only known risk factor so far is the mother's age. The risk of conceiving a child with Down syndrome is 0.11 percent for women at age 30. This risk increases to 0.3 percent and 1 percent for women at ages 35 and 40, respectively.
Effects
Children with Down syndrome share similar physical features: flat facial profile, protruding tongue, slanted eyes, small ears. These children tend to reach developmental milestones like crawling, walking and talking much later than normal children.
However, children with Down syndrome are able to learn and develop various skills, only at much slower rate than children without it.
Significance
One of the major issues for children with Down syndrome is long-term medical care. About 40 to 50 percent of children with Down syndrome have heart defects. They are also more likely to develop pulmonary hypertension and lung defects. About 50 percent of children with Down syndrome have hearing loss and vision issues. They also tend to have higher rates of obesity and gastrointestinal issues.
Identification
Down syndrome can be diagnosed during pregnancy using a screening test and a diagnostic test. A screening test, such as a nuchal translucency test, genetic ultrasound, or percutaneous umbilical blood sampling, can tell you the risk of a fetus having Down syndrome. A diagnostic test can tell you with 99 percent accuracy whether the fetus actually has Down syndrome.
The American College of Obstetrics and Gynecology recommends screening tests for Down syndrome for all pregnant women of all ages.
Warning
Diagnostic testing conducted inside the fetus has been shown to increase the risk of miscarriage and a host of pregnancy complications. It is recommended that diagnostic tests only be performed for women at high risk of having a fetus with Down syndrome, including women aged 35 and older, women with a family history of genetic defects, or women with a positive result from a screening test.
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