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What Is Down Syndrome?

Down syndrome is a condition in which a baby is born with an extra number 21. The extra chromosome is associated with delays in the child’s mental and physical development, as well as an increased risk for health problems.

The physical features and medical problems linked to Down syndrome can vary widely from child to child. While some kids need a lot of medical attention, others lead healthy lives.

Down syndrome, also called trisomy 21, happens by chance, can’t be prevented, and isn’t caused by anything a parent did or didn't do. Fortunately, the health problems can be managed well, especially when found early, and many resources are available to help kids and their families.

What Causes Down Syndrome?

A baby inherits genetic information from its parents in 46 chromosomes, typically 23 from the mother and 23 from the father. Chromosomes hold our genes, which carry the information that determine how our bodies look and work, including traits from our relatives like hair and eye color.

In most cases of Down syndrome, a child gets an extra chromosome 21 — for a total of 47 chromosomes instead of 46. Rarely, the extra chromosome 21 attaches to another chromosome. This extra genetic material causes the physical features and developmental delays in people with Down syndrome. The features are no different if the extra chromosome is by itself or attached to another one.

How Can Down Syndrome Affect Kids?

Kids with Down syndrome often have similar physical features, such as a flat facial profile, an upward slant to the eyes, small ears, and a tongue that tends to stick out.

Low muscle tone (called hypotonia) is also common in kids with Down syndrome but is less obvious as they get older. Children will reach developmental milestones, like sitting up, crawling, and walking, though typically later than other kids do. Low muscle tone may also contribute to sucking and feeding problems during early childhood, as well as gastroesophageal reflux and constipation.

At birth, babies with Down syndrome are often smaller than other newborns, and they tend to grow at a slower rate and remain shorter than their peers. Toddlers and older kids may have delays in speech and self-care skills like feeding, dressing, and using the toilet.

Down syndrome affects kids' ability to learn in different ways, and most have mild to moderate intellectual disability. Kids can and do learn, and they can develop skills throughout their lives. They just reach goals at a different pace. So it is important to remember that each child with Down syndrome will gain skills in their own time and to not compare them to their typical peers or even kids with the same condition.

Kids with Down syndrome have a wide range of abilities, and there's no way to tell at birth what they can do as they grow up.

What Medical Problems Can Happen With Down Syndrome?

Some kids with Down syndrome have no serious health problems. But others may have medical issues that need extra care. Many go to clinics that specialize in caring for people with Down syndrome. If you don’t have a Down syndrome clinic in your area, your primary care doctor can help coordinate care for your child.

Almost half of all children born with Down syndrome will have a congenital heart defect. All newborns with Down syndrome should be checked for this with a specialized ultrasound for the heart (echocardiogram).

About half of all kids also have problems with hearing and vision. Hearing loss can be related to fluid buildup in the inner ear or to structural problems of the ear itself. Vision problems commonly include strabismus (eyes do not track together), nearsightedness or farsightedness, and cataracts.

Vison and hearing problems can affect language and learning. Regular checkups by an otolaryngologist (ear, nose, and throat doctor), audiologist, and an ophthalmologist can find and manage any problems.

Children may need to see other medical specialists, depending on their needs. Medical problems that happen more often with Down syndrome include:

People with Down syndrome sometimes have an unstable upper spine (neck) and should be checked by a doctor every year or sooner if they have symptoms, such as neck pain, changes to their walking, or unexpected loss of bladder or bowel control. Some children may need neck X-rays before playing some sports or before getting anesthesia.

How Is Down Syndrome Diagnosed?

Two types of prenatal tests can look for Down syndrome in a fetus:

  • Screening tests estimate the chances that a fetus has Down syndrome.
  • Diagnostic tests can tell if the fetus does have the condition.

Screening tests are cost-effective and easy to do. But they don't give a definitive answer about whether a baby has Down syndrome. So these tests are used to help parents decide whether to have more diagnostic tests.

Diagnostic tests accurately diagnose Down syndrome and other chromosomal problems. But because this involves getting some of the baby’s cells while still inside the uterus, there is a risk of miscarriage and other complications.

If you're unsure about which test, if any, is right for you, your doctor or a genetic counselor can help you sort through the pros and cons of each.

Screening tests include:

  • nuchal translucency testing: This test is done between weeks 11–14 of pregnancy. It uses ultrasound to measure the clear space in the folds of tissue behind a developing baby's neck. Babies with Down syndrome and other chromosomal problems tend to have fluid buildup there, making the space look larger. To calculate the odds that the baby has Down syndrome, doctors use this measurement, along with the mother's age (the risk for a baby to have Down syndrome increases with the mother’s age), and the baby's gestational age.
  • the triple screen or quadruple screen (also called the multiple marker screen)
  • integrated screen: This uses results from first-trimester screening tests (with or without nuchal translucency) and blood tests with a second trimester quadruple screen to come up with the most accurate screening results.
  • an ultrasound
  • cell-free fetal DNA analysis: This test analyzes fetal DNA found in the mother’s blood. It can be done in the first trimester and is more sensitive at finding trisomy 21 than standard the screening tests noted above.

Diagnostic tests include:

If the doctor suspects Down syndrome after a baby is born, a (chromosome analysis) can confirm the diagnosis. This is typically done on a blood sample and the chromosomes are grouped by size, number, and appearance to look for differences.

How Can Parents Help?

If your child has Down syndrome, you may at first have feelings of loss, guilt, and fear of the unknown. Talking with other parents of kids with Down syndrome may help you deal with your concerns and find ways to look toward the future. Many parents find that learning as much as they can about the condition helps ease fears.

Children with Down syndrome benefit from getting early intervention services as soon as possible. Physical therapy, occupational therapy, and speech/feeding therapy can help, and early childhood educators can work with your child to encourage and boost development.

States provide early intervention services to kids with disabilities from birth to age 3. Check with a health care provider — a doctor, nurse, developmental pediatrician, or a social worker — to find resources in your area.

When kids with Down syndrome turn 3 years old, they’re guaranteed educational services under the Individuals with Disabilities Education Act (IDEA). Under IDEA, local school districts must provide "a free appropriate education in the least restrictive environment" and an individualized education program (IEP) for each child.

Where to send your child to school can be a hard decision. The needs of some kids with Down syndrome are best met in a specialized program. But many kids with Down syndrome go to a typical school and enjoy the same activities as other kids their age. Being in a regular classroom (known as inclusion), when appropriate, is good for both the child with Down syndrome and the other kids.

A few kids with Down syndrome go on to college. Many transition to semi-independent living. Others continue to live at home but hold jobs and find their own success in the community.

Your school district's child study team can work with you to find what's best for your child. All decisions about your child’s education should involve your input, as you are your child's best advocate.

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Medically reviewed by: Nina Powell-Hamilton, MD
Date reviewed: February 2022