Down syndrome is a condition in which a baby is born with an
extra chromosome. Chromosomes are small “packages” of genes in the
body. They determine how a baby’s body forms during pregnancy and
how, as the baby grows in the womb and after birth, the baby’s body
functions. Normally, a baby is born with 46 chromosomes. Babies born
with Down syndrome have an extra copy of one of these chromosomes.
This extra copy changes the body’s and brain’s normal development
and causes mental and physical problems for the baby.
Even though people with Down syndrome might have some physical and
mental features in common, symptoms of Down syndrome can range from
mild to severe. Usually, mental development and physical development
are slower in people with Down syndrome than in those without it.
Some common physical signs of Down syndrome include:
- A flat face with an upward slant to the eye, a short neck,
small ears, and a large tongue
- Tiny white spots on the iris (colored part) of the eye
- Small hands and feet
- A single crease across the palm of the hand
- Small pinky fingers that sometimes curve toward the thumb
- Poor muscle tone or loose ligaments
To learn more about Down Syndrome click on one of the following
links or scroll down the page.
What We Know About Down Syndrome
- How often does Down syndrome occur?
- What problems do children with Down syndrome have?
What We Still Do Not Know About Down
Syndrome
- What causes Down syndrome?
- Can Down syndrome be prevented?
Resources for Families and Individuals
Affected by Down Syndrome
What
We Know About Down Syndrome |
How often does Down syndrome occur?
CDC estimates that each year about 3,357 babies in the United
States are born with Down syndrome (1). In other words, about 13 of
every 10,000 babies born in the United States each year is born with
Down syndrome.
What problems do children with Down syndrome have?
Babies and adults with Down syndrome can have physical problems,
as well as intellectual disabilities. Every baby born with Down
syndrome is different. In addition to the physical signs, some might
have major birth defects or other medical problems. However, many
people with Down syndrome live happy, productive lives well into
adulthood.
Still, some physical problems associated with Down syndrome
include:
- A birth defect of the heart
- Stomach problems, such as a blocked small intestine
- Celiac disease, a digestive disease that damages the small
intestine so that nutrients from food are not absorbed well
- Problems with memory, concentration, and judgment, often
called dementia
- Hearing problems
- Eye problems, such as cataracts or trouble seeing objects
that are close by (far-sighted)
- Thyroid problems
- Skeletal problems
A person with Down syndrome can have an IQ in the
mild-to-moderate range of mental retardation. He or she also mighty
have delayed language development and difficulties with physical
coordination.
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What
We Still Do Not Know About Down Syndrome |
What causes Down Syndrome?
To understand Down syndrome, it is necessary to understand how a
baby develops. Each baby starts developing when he or she receives
23 chromosomes from the mother’s egg and 23 chromosomes from the
father’s sperm. When a baby has Down syndrome, an error happened
when either the egg or the sperm was formed. This error caused an
extra chromosome (called chromosome number 21) in the egg or sperm,
so that the baby received a total of 24 instead of 23 chromosomes
from one of its parents. Therefore, the baby ends up having 47
chromosomes in every cell of his or her body, instead of 46
chromosomes. This extra chromosome causes the physical signs and
additional problems that can occur among people with Down syndrome.
The causes of the errors that produces the extra chromosome is not
known.
The age of the mother is the only factor that has been shown to
increase the risk of having a baby with Down syndrome. This risk
increases with every year, especially after the mother is 35 years
of age. However, because younger women are more likely to have
babies than older women, 80% of babies with Down syndrome are born
to women younger than 35 years of age.
CDC works with many researchers to study the risk factors that
can increase the chance of having a baby with Down syndrome.
Following are examples of what this research has found:
- The number of babies with Down syndrome seems to be
increasing, especially among mothers older than 35 years of age
(2).
- Certain factors seem to influence how long a person with
Down syndrome will live, including ethnicity, low weight at
birth, and whether the baby was born with a heart defect (3).
- Death rates among Black or African-American infants with
Down syndrome seem to be higher than death rates among White
infants with Down syndrome (4).
Can Down Syndrome be prevented?
There is no known way to prevent the Down syndrome. However,
infants and children with Down syndrome often will benefit from
special programs that help to improve their physical and mental
limitations. These include speech therapy, occupational therapy, and
exercises for physical coordination. Children with Down syndrome
usually also need extra help or attention in school.
While there is currently no way to prevent Down syndrome, mothers
can take steps before and during pregnancy to have a healthy
pregnancy. Steps include taking a daily multivitamin with folic acid
(400 micrograms), not smoking, and not drinking alcohol during
pregnancy.
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Resources for Families and Individuals Affected by Down
Syndrome |
National Down Syndrome Society
National Association for Down Syndrome
Medline
Mayo Clinic
References
- Canfield MA, Honein MA, Yuskiv N, Xing J, Mai CT, Collins
JS, et al. National estimates and race/ethnic-specific variation
of selected birth defects in the United States, 1999-2001. Birth
Defects Res A. 2006;76(11): 747-56.
- Besser LM, Shin M, Kucik JE, & Correa A. Prevalence of Down
syndrome among children and adolescents in metropolitan Atlanta.
Birth Defects Res A. 2007;79: 765-74.
- Rasmussen SA, Lee-Yang Wong MS, Correa A, Gambrell D, and
Friedman JM. Survival in infants with Down syndrome,
metropolitan Atlanta, 1979-1998. Pediatrics. 2006;148: 806-12.
- Shin M, Kucik JE, Correa A. Causes of death and case
fatality rates among infants with Down syndrome in metropolitan
Atlanta. Birth Defects Res A. 2007;79: 775-80.
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Date:
March 11, 2009
Content source: National Center on Birth Defects and Developmental
Disabilities