What is Down Syndrome?

Down syndrome is a chromosomal abnormality that occurs approximately once in 800 live births. It occurs in all cultures, ethnic groups, socioeconomic levels and geographic regions. It appears in both boys and girls with equal frequency. Individuals with Down syndrome are identified at birth by certain physical characteristics that can include reduced muscle tone, skin folds covering the inner corners of the eyes, a flat nasal bridge, a shortened neck, and smaller hands with a single crease in the palm. All persons with Down syndrome will have some degree of mental retardation, and according to current medical research, usually in the mild to moderate range.

Nothing that parents do before or during pregnancy causes Down syndrome. Nor is it preventable. The physical characteristics and developmental delay observed in individuals with Down syndrome are due to the presence of an extra chromosome. Normally there are 46 chromosomes in each cell, arranged in 23 pairs. With Down syndrome the 21st pair has a third chromosome attached. This additional chromosome causes a genetic imbalance, altering the normal course of development. Because all the other chromosomes function normally, most characteristics, both physical and cognitive, are determined by the remaining forty-six in the genetic blue-print of the individual with Down syndrome.

For a more complete description of Down syndrome plus a guide for parents of children with Down syndrome, the following references may be helpful:

Stray-Gundersen, Karen, Babies with Down Syndrome, A New Parent Guide, Woodbine House, Inc. 1986.

Lott, Ira T., McCoy, Ernest E., Down Syndrome, Advances in Medical Care, John Wiley and Sons, Inc. 1992.