Understanding Down Syndrome -- Diagnosis and Treatment

How Do I Know If My Child Has Down Syndrome?

When a couple is having a baby, there’s a lot to think about, including whether the infant may have a condition. For Down syndrome, there are two types of tests: One tells you the baby’s risk, and the other diagnoses Down syndrome.

Screening Tests

Screening tests can estimate the chance that your baby may have Down syndrome, but they can’t tell you for sure if your baby has it or not. Your results should be explained to you as, “You have a 1 in 1,000 chance of having a baby with Down syndrome,” or “Your baby has a 1 in 250 chance of having Down syndrome.”

There are several screening tests for Down syndrome. All measure things in the mother’s blood.

Doctors may look at the blood test along with findings from ultrasound images of the developing baby. Certain measurements, such as extra fluid at the back of the baby’s neck, can suggest your baby might have Down syndrome.

Screening tests include:

Combined first trimester screen: This test is usually done between 9 and 13 weeks of pregnancy. It’s a blood test that measures levels of a certain pregnancy hormone and a protein made by the unborn baby and mother, along with an ultrasound. When looked at together, this screening test is about 82% to 87% accurate.

Second trimester triple screen: This blood test measures hormone and protein levels along with estriol, a hormone made by the mother and the unborn baby. It’s about 69% accurate.

Second trimester quad screen. This blood test combines the triple screen with a test that looks at another hormone made by the placenta called inhibin-A. It can accurately predict about 81% of Down syndrome cases.

Integrated screening. This includes the combined first trimester screen and the second trimester quad screen. Together, this combination can identify about 94% to 96% of cases of Down syndrome.

Another screening test appears to be more accurate than the others. Called cell-free DNA (cfDNA), it finds small fragments of fetal DNA floating in the mother’s blood and tests them. It can be done after 10 weeks of pregnancy. But these tests are still in development and can sometimes give false results.

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Diagnostic Tests

Diagnostic tests use a direct sample of the baby’s genetic material. They can tell with almost 100% accuracy whether or not your baby has Down syndrome.

If a screening test shows an increased chance of Down syndrome, you may choose to have a diagnostic test during pregnancy. You can also request a diagnostic test without having a screening. Unlike screening tests, these tests have a small chance of harming babies still in the womb. A needle needs to be inserted in the mother’s womb to collect the material for testing. This raises the risk of miscarriage (the risk ranges from less than 1% to around 2%,).

A baby can have diagnostic testing after delivery, too.

The different diagnostic tests during pregnancy are:

Amniocentesis: This test cannot be performed before the 14th week of pregnancy. It's usually done between weeks 14 and 18. It uses a sample of the fluid in the mother’s womb.

Chorionic villus sampling: This test takes a sample from the placenta. It's performed between 9 and 11 weeks of pregnancy.

Percutaneous umbilical blood sampling (PUBS): This test takes a sample of the baby’s blood from the umbilical cord. It is the most accurate of the three tests, but it can't be performed until you are at least 18 weeks pregnant.

After you have your baby, a doctor will do a physical exam and test the baby’s blood to diagnose Down syndrome.

A genetic counselor can help you understand the results of your tests.

What You Need to Know

Down syndrome happens at the time of pregnancy. Nothing you do or don’t do while pregnant can cause it. People with this condition have an extra chromosome, the part of a cell that has genes.

The risk of having a baby with the condition goes up with the mother’s age. At age 20, a woman has a 1 in 2,000 chance of having a baby with Down syndrome. By age 35, that risk is 1 in 350.

Very few cases of Down syndrome -- only about 1% -- are “hereditary,” or passed down from a parent to their child through the genes. If your sister or brother, aunt or uncle has Down syndrome, there’s very little chance you’ll have a baby with it. But if a woman has had a baby with Down syndrome, her chance of having another child with the condition is higher.

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What Are the Treatments for Down Syndrome?

There's no cure for Down syndrome. But children with the condition can lead happy, productive lives. Everyone born with the syndrome has some trouble learning, but just like other children, kids with Down syndrome can learn basic skills -- sitting, walking, talking, and self-care (such as toilet training and bathing). It just may take them longer. Physical therapy begun shortly after birth can help strengthen muscles for these basic motor skills.

Regular medical care to treat the chronic health problems linked to Down syndrome is also important. A child with the syndrome should have regular eyesight and hearing tests, be evaluated for thyroid problems, and get regular childhood immunizations.

Children with Down syndrome attend school, and many join regular classes. There are laws to help a child with Down syndrome get special placement or extra help. They can, and do, take an active part in various activities in their communities.

Some adults with Down syndrome live with their families. Some live in group homes with other people with Down syndrome. Others live independently. Many people with Down syndrome hold jobs. The opportunities for people with Down syndrome are great, and there is no reason not to expect them to make lasting, positive contributions to society.

For more information about Down syndrome and raising a child with the condition, ask your doctor about resources in your community, and check out the web site of the National Down Syndrome Society.

WebMD Medical Reference Reviewed by Hansa D. Bhargava, MD on April 28, 2015

Sources

SOURCES:

National Down Syndrome Society: "What is Down Syndrome?"

National Institute of Child Health and Human Development: "How do health care providers diagnose Down syndrome?"

CDC: "Facts About Down Syndrome."

American College of Obstetricians and Gynecologists: "Screening Tests for Birth Defects FAQ."

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