Down syndrome is a genetic problem. It is also called trisomy 21. It includes certain birth defects, learning problems, and facial features. A child with Down syndrome also may have heart defects and problems with vision and hearing. How severe or mild these problems are varies from child to child.

Down syndrome is one of the most common genetic birth defects. It affects about 1 out of 700 babies. Adults with Down syndrome may live about 60 years, but this can vary.

An egg cell and sperm cell typically start with 46 chromosomes. The egg and sperm cells then divide, and their number of chromosomes decreases by half. The egg and sperm cells then have 23 chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby will then have a complete set of 46 chromosomes. Half are from each birth parent.

But sometimes an error occurs when the 46 chromosomes are being divided by half. An egg or sperm cell may keep both copies of chromosome number 21, instead of just one copy. If this egg is fertilized or if this sperm fertilizes an egg, then the baby will have three copies of chromosome number 21 (47 chromosomes total). This is called trisomy 21.

Sometimes the extra chromosome 21 or part of it is attached to another chromosome in the egg or sperm. This is called a translocation and can also cause Down syndrome. This is the only form of Down syndrome that may be inherited from a parent.

A rare form of Down syndrome is called mosaic trisomy 21. This is when an error in the division of the chromosomes happens after fertilization. People with this syndrome have cells with the typical number of chromosome (46) and some cells with an extra chromosome number 21.

The age you are when you give birth is a factor linked to the risk of having a baby with Down syndrome. This risk increases with each year of age, especially after age 35. But younger people are more likely to have babies than older people. So most babies with Down syndrome are born to those who are younger than 35.

Symptoms can occur differently in each child. They can include:

• Eyes that slant upward.
• Small ears that may fold over slightly at the top.
• Small mouth that makes the tongue seem large.
• Small nose with a flattened bridge.
• Short neck.
• Small hands with short fingers.
• Two instead of three palm creases, including one across the palm and one around the base of the thumb.
• Short height.
• Loose joints due to reduced muscle strength.

Most children with Down syndrome will have some but not all of these features.

Down syndrome can also include:

• Heart defects.
• Intestinal problems.
• Vision problems.
• Hearing problems.
• Thyroid problems.
• Blood conditions, such as leukemia, and risk for infections.
• Learning problems.

Chromosome problems, such as Down syndrome, can often be diagnosed before birth. Screening tests are often done first. These often combine a blood test with an ultrasound. A screening test tells you and your doctor if you have a greater or lesser chance of having a child with Down Syndrome. This test doesn't determine a diagnosis. A diagnostic test is more invasive and can be risky. But it generally can find the problem.

The most common screening test that occurs to find Down syndrome during a pregnancy is called noninvasive prenatal screening. This blood test looks for pieces of chromosome 21 that may come from the placenta. Fetal ultrasound during pregnancy can also show the possibility of Down syndrome. But ultrasound is not 100% accurate. Problems from Down syndrome may not be seen with ultrasound.

Diagnostic tests are done by looking at cells in the amniotic fluid or from the placenta. These tests include:

• Chorionic villus sampling. This test examines cells from the placenta.
• Amniocentesis. This tests the fluid from the sac surrounding the baby (amniotic fluid).
• Percutaneous umbilical blood sampling. This tests blood from the umbilical cord.

All three of these tests look for characteristic changes in the chromosomes that occur in a Down syndrome diagnosis.

After birth, your baby may be diagnosed with a physical exam. The doctor may also take a blood sample. This is checked in a lab to look for the extra chromosome.

There is no cure for Down syndrome. But a child with Down syndrome may need treatment for problems, such as:

• Heart defects. About half of babies with Down syndrome have heart defects. Some defects are minor. These can be treated with medicines, or they will fix themselves on their own. Other babies may need surgery. All babies with Down syndrome should have an echocardiogram (heart ultrasound) and be looked at by a pediatric cardiologist. This exam and test should be done shortly after birth. This is so that any heart defects can be found and treated correctly.
• Intestinal problems. Some babies with Down syndrome are born with intestinal problems that need surgery.
• Vision problems. Common problems include crossed eyes, nearsightedness or farsightedness, and cataracts. Most eyesight problems can be made better with eyeglasses, surgery, or other treatments. Your child should see an eye care doctor (pediatric ophthalmologist) before age 1 year.
• Hearing loss. This is caused by fluid in the middle ear, a nerve defect, or both. Your child should get regular hearing tests so that any problems can be treated early. This will help with language development.
• Other health problems. Children with Down syndrome may have thyroid problems and leukemia. They also tend to have many colds, as well as bronchitis and pneumonia. Your child should get regular medical care and stay up to date on vaccines.
• Learning problems. These vary widely from child to child. They can be mild, moderate, or severe. But most learning problems are mild to moderate. Many children will receive early intervention and special education.

Some people claim that giving high-dose vitamins to children with Down syndrome will improve their learning and development problems. No studies have proved that this works.

Talk with your child's doctors about the risks, benefits, and possible side effects of all treatments.

Complications of Down syndrome vary depending on what body organ is affected and how severe the problem is. Problems include certain birth defects, learning problems, and facial features. A child with Down syndrome also may have heart defects and problems with vision and hearing. How bad the complications are varies from child to child. Treatment will also vary depending on what body organ is affected and how bad the problem is. Your child's doctor will discuss treatment choices with you.

Researchers don't know how to prevent the chromosome errors that cause this problem. There is no reason to believe that birth parents can do anything to cause or prevent Down syndrome in their child.

For those who have given birth to a child with Down syndrome, the chance of having another baby with Down syndrome depends on several things. Age is a factor. Most babies with Down syndrome are born to those younger than age 35. This is because those younger than 35 have more babies than those older than 35.

Your doctor may refer you to a genetic counselor. This expert can explain the results of chromosome tests in detail. They can talk about risks for future pregnancies and what tests are available to diagnose chromosome problems before a baby is born.

Some medical organizations advise that all those of any age who are pregnant be offered screening for Down syndrome. Talk with your doctor about this prenatal screening test.

Children with Down syndrome can often do most things that any young child can do. They can walk, talk, dress themselves, and be toilet trained. But they often do these things at a later age than other children. The exact ages of these development milestones are different for each child. Early intervention programs that begin when a child is a baby can help the child reach their potential.

A child with Down syndrome can go to school. Special programs beginning in the preschool years help children with Down syndrome develop skills as fully as possible. Many children are helped with early intervention and special education. They can also enter a regular classroom. Many children will learn to read and write. They can take part in childhood activities, both at school and in their community.

Your child may need physical, occupational, and speech therapy to help with their development. Talk with your child's doctor, other families, and national Down syndrome support agencies to learn what to expect with Down syndrome. You can also learn what may be helpful in raising a child with Down syndrome.

Special work programs are designed for adults with Down syndrome. Many can hold regular jobs. More and more adults with Down syndrome live semi-independently in community group homes. They take care of themselves, do household chores, develop friendships, do leisure activities, and work in their communities.

Some people with Down syndrome marry. Most men with Down syndrome can't father a child. In any pregnancy, a woman with Down syndrome has a 1 out of 2 chance of conceiving a child with Down syndrome. Many of the pregnancies are miscarried. Talk to your doctor if you have questions about your child's ability to have children in the future.

Contact the doctor if your child has:

• Symptoms that don't get better, or that get worse.
• New symptoms.

• Down syndrome is a genetic problem. It includes certain birth defects, learning problems, and facial features. A child with Down syndrome also may have heart defects and problems with vision and hearing.
• The age you are when you give birth is a factor linked to the risk of having a baby with Down syndrome. This risk increases with each year of age, especially after age 35.
• There is no reason to believe that anything can be done to cause or prevent Down syndrome in a child. Researchers don't know how to prevent the chromosome errors that cause this problem.
• Down syndrome can often be diagnosed before birth. After birth, your baby may be diagnosed with a physical exam and testing to look at their chromosomes.
• There is no cure for Down syndrome, but treatment is available to help your child.
• Your child may need physical, occupational, and speech therapy to help with their development. Many children are helped with early intervention and special education.

Tips to help you get the most from a visit to your child's doctor:

• Know the reason for the visit and what you want to happen.
• Before your visit, write down questions you want answered.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new directions your doctor gives you for your child.
• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
• Ask if your child's condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if your child does not take the medicine or have the test or procedure.
• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your child's doctor after office hours. This is important if your child becomes ill and you have questions or need advice.