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Down Syndrome

Reviewed by: Mary L. Gavin, MD
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What Is Down Syndrome?

Down syndrome is a condition in which a baby is born with an extra chromosome. The extra causes delays in the way a child develops, mentally and physically.

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, can't be prevented. But the health problems that may happen can be treated, and many resources are available to help kids and their families.

What Causes Down Syndrome?

Normally, at the time of conception a baby inherits genetic information from its parents in 46 chromosomes: 23 from the mother and 23 from the father. Chromosomes contain hundreds, or even thousands, of genes. Genes carry the information that determine traits passed on from our parents (like hair or eye color).

In most cases of Down syndrome, a child gets an extra chromosome 21 — for a total of 47 chromosomes instead of 46. Sometimes, only part of chromosome 21 attaches to another chromosome. This extra genetic material causes the physical features and developmental delays in Down syndrome.

No one knows for sure why the condition happens and there's no way to prevent the chromosomal error that causes it.

How Can Down Syndrome Affect Kids?

Kids with Down syndrome tend to share physical features such as a flat facial profile, an upward slant to the eyes, small ears, and a tongue that sticks out.

Low muscle tone (called hypotonia) is also common in kids with Down syndrome. Though this can and often does improve over time, most children will reach developmental milestones — like sitting up, crawling, and walking — later than other kids. Low muscle tone may also contribute to sucking and feeding problems, as well as gastroesophageal reflux and constipation.

At birth, kids with Down syndrome are smaller than other newborns, and they tend to grow at a slower rate and remain smaller 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, but most have mild to moderate intellectual disability. Kids can and do learn, and can develop skills throughout their lives. They just reach goals at a different pace. So it's important not to compare a child with Down syndrome to typically developing siblings or even other children with the 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 a mix of medical issues that need extra care. Many go to clinics that specialize in caring for those with Down syndrome. If you don’t have a Down syndrome clinic in your area, your doctor will help coordinate care for your child.

Almost half of all children born with Down syndrome will have a congenital heart defect. All infants with Down syndrome should be checked by a pediatric cardiologist.

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 don’t line up), 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 correct any problems.

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

  • thyroid problems
  • stomach and intestinal problems, including celiac disease
  • seizures
  • breathing problems, including sleep apnea and asthma 
  • obesity
  • infections, including ear infections and pneumonia
  • childhood leukemia 

People with Down syndrome sometimes have an unstable upper spine and should be checked by a doctor every year or sooner if they have symptoms, such as neck pain, walking funny, or 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:

  1. Screening tests estimate the chances that a fetus has Down syndrome.
  2. Diagnostic tests can tell if the fetus actually has the condition.

Screening tests are cost-effective and easy to do. But they can'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 they're done inside the uterus, so 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 (pregnant women age 35 and older are more likely to have a baby with Down syndrome), and the baby's gestational age.
  • the triple screen or quadruple screen (also called the multiple marker test)
  • 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 DNA. This test analyzes fetal DNA found in the mother’s blood. It can be done in the first trimester and is more accurate at finding trisomy 21 than standard blood tests. Currently, cell free DNA testing is only offered to women with a higher risk of having a baby with Down syndrome.

Diagnostic tests include:

If the doctor suspects Down syndrome after a baby is born, a karyotype — a blood or tissue sample stained to show chromosomes grouped by size, number, and shape — can verify the diagnosis.

How Can Parents Help?

If your child has Down syndrome, you may at first have feelings of loss, guilt, and fear. 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 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 your doctor, developmental pediatrician, or a social worker to find resources in your area.

When a child is 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 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.

You also can find more information and support online at:

Reviewed by: Mary L. Gavin, MD
Date reviewed: January 2021