Down Syndrome | Diagnosis & Tests

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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.

Bibliography

See a list of resources used in the development of this information.

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.

Written by familydoctor.org editorial staff

Reviewed/Updated: 02/14
Created: 01/99

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