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What is Down syndrome?

Down syndrome is a genetic disorder that causes mental retardation and physical defects. It is caused by the presence of an extra copy of chromosome number 21. This condition is called trisomy 21.


What are the physical signs and birth defects of Down syndrome?

Some of the most common physical signs of Down syndrome are upward slanting eyes, flattened facial features, ears that are small or unusually shaped, broad hands with short fingers and curved "pinky" fingers, and a small head. None of these physical differences cause health problems.

Some birth defects associated with Down syndrome cause more serious health problems. Babies who have Down syndrome often have poor muscle tone or problems with their heart, stomach or eyes. Intelligence ranges from low normal to very retarded (slow to learn), which can make learning and development more difficult.

Causes & Risk Factors

Are some people more likely than others to have a baby who has Down syndrome?

If you have already had a baby who has Down syndrome, you are more likely to have another one. For every 100 couples who have another baby, 1 will have another who has Down syndrome. If you have been diagnosed with a chromosomal abnormality, you also have an increased risk of having a baby who has Down syndrome.

Additionally, the risk of Down syndrome increases with the age of the mother, as shown in this table:

Risk of Down Syndrome

Mother's age

Chance of having a baby with Down syndrome

20 years

1 in 1,667

25 years

1 in 1,300

30 years

1 in 950

35 years

1 in 365

40 years

1 in 100

45 years

1 in 30

Diagnosis & Tests

How is Down syndrome diagnosed?

To find out if a baby has Down syndrome before birth, tests (such as amniocentesis and chorionic villus sampling) can check the tissue and fluid in the womb for the extra chromosome. However, there is a slight risk that these tests can cause a miscarriage. Therefore, these tests are used only when there is a high chance of a genetic problem in the baby (such as a mother 35 years of age or older).After birth, if the baby has any of the physical signs or birth defects of Down syndrome, your doctor can test the baby's blood for the extra chromosome.

Is there another way to tell if my baby might have Down syndrome?

A blood test called a triple screen (also called a quad marker screen if combined with other tests) can be done between the 15th and the 22nd weeks of pregnancy. However, the test is most accurate when done between the 16th and 18th weeks. The screen cannot tell for sure whether your baby has Down syndrome or other chromosomal disorders, but it can tell if the risk is higher. If the test is positive, it means your risk of having a baby who has Down syndrome is higher. But remember that many women with a positive screen have babies that do not have Down syndrome.

A negative screen means that the chance of Down syndrome is low. However, it doesn't guarantee that a baby doesn't have Down syndrome.

Should I be tested?

This decision is up to you. Some women feel better if they know their risk so that they can prepare themselves for the possibility of having a baby who has Down syndrome. Your doctor can help you understand your risks and consider the pros and cons of getting tested.


Will my child need special medical care?

You may need to give your baby medicine. Your doctor will probably want to check your baby often to be sure that he or she is growing well and isn't developing problems from birth defects.

Your baby may need to have physical therapy every week to help with building up muscle tone and coordination. Later on, speech therapy and occupational therapy (to help with issues such as language skills, hand-eye coordination and social skills) may be helpful for your child.

As with any child, children who have Down syndrome need regular medical care. Because children with Down syndrome often have problems hearing and seeing, your doctor may want to test your child for these problems at each visit. If there's a problem, your doctor may refer your child to a specialist who can help him or her.


What are the health problems that might affect my baby?

Some babies who have Down syndrome have poor muscle tone. This makes it harder for them to learn to roll over, sit up and walk. Physical therapy can help with these problems.

About half of babies who have Down syndrome also have a heart problem. An ultrasound exam of your baby's heart will show any defects. Surgery may be necessary to fix the heart problems associated with Down syndrome.

Some babies who have Down syndrome have problems swallowing, or they may have blockages in their intestines. Surgery may be necessary to fix these problems. Once they are fixed, they usually cause no further harm.

Some babies have eye problems, such as cataracts (cloudy lenses) or crossed eyes. Corrective lenses or surgery may be necessary to fix these problems.

Children who have Down syndrome may have colds, ear infections and sinus infections more often than other children. They are more likely to have thyroid problems, hearing loss, seizures and problems in their bones and joints. It's also common for these children to be late in teething.

Will my child have learning problems?

At birth, it isn't possible to tell how smart a baby who has Down syndrome will be. Intelligence ranges from low normal to very retarded (slow to learn) in people who have Down syndrome. If you keep your child physically healthy and provide therapy or treatment for his or her impairments, he or she will be better able to learn. With therapy, many children who have Down syndrome grow up to have jobs and live independently.


Some of this content was developed by the University Centers for Excellence in Developmental Disabilities in CA (USC), MA (UMass Boston), IA (U of IA), KY (U of KY) and supported in part by the National Center on Birth Defects and Developmental Disabilities (NCBDDD) of the Center for Disease Control and Prevention through a cooperative agreement with Association of University Centers on Disabilities (AUCD). The opinions expressed are strictly those of the authors and do not necessarily reflect the opinions of the supporting organizations.