Down syndrome (DS), also called Trisomy 21, is a condition in which extra genetic material causes delays in the way a child develops, both mentally and physically. It affects about 1 in every 800 babies.
The physical features and medical problems associated with Down syndrome can vary widely from child to child. While some kids with DS need a lot of medical attention, others lead healthy lives.
Though Down syndrome can't be prevented, it can be detected before a child is born. The health problems that may go along with DS can be treated, and many resources are available to help kids and their families who are living with the condition.
What causes Down Syndrome.
Normally, at the time of conception a baby inherits genetic information from its parents in the form of 46 chromosomes: 23 from the mother and 23 from the father. In most cases of Down syndrome, a child gets an extra chromosome 21 — for a total of 47 chromosomes instead of 46. It's this extra genetic material that causes the physical features and developmental delays associated with DS.
Although no one knows for sure why DS occurs and there's no way to prevent the chromosomal error that causes it, scientists do know that women age 35 and older have a significantly higher risk of having a child with the condition. At age 30, for example, a woman has about a 1 in 1,000 chance of conceiving a child with DS. Those odds increase to about 1 in 400 by age 35. By 40 the risk rises to about 1 in 100.
How Down Syndrome affects children.
Children with Down syndrome tend to share certain physical features such as a flat facial profile, an upward slant to the eyes, small ears, and a protruding tongue.
Low muscle tone (called hypotonia) is also characteristic of children with DS, and babies in particular may seem especially "floppy." Though this can and often does improve over time, most children with DS typically reach developmental milestones — like sitting up, crawling, and walking — later than other children.
At birth, children with DS are usually of average size, but they tend to grow at a slower rate and remain smaller than their peers. For infants, low muscle tone may contribute to sucking and feeding problems, as well as constipation and other digestive issues. Toddlers and older children may have delays in speech and self-care skills like feeding, dressing, and toilet teaching.
Down syndrome affects children’s' ability to learn in different ways, but most have mild to moderate intellectual impairment. Children with DS can and do learn, and are capable of developing skills throughout their lives. They simply reach goals at a different pace — which is why it's important not to compare a child with DS against typically developing siblings or even other children with the condition.
Children with DS have a wide range of abilities, and there's no way to tell at birth what they will be capable of as they grow up.