A New Blood Test for Down's Syndrome

by Pattie Hughes | More from this Blogger

Diagnosing Down's syndrome has just gotten easier. Researchers at Stanford University, Howard Hughes Medical Institute and Lucile Packard Hospital have developed a maternal blood test that offers a non invasive way to detect Down's syndrome and other chromosome disorders in the fetus.

There is currently a blood screening test done during pregnancy to check for Down's syndrome. This is called the alpha feto protein, triple screen or quad screen and is done in the early second trimester. However, this is merely a screening tool and doesn't offer a definitive diagnosis. It only shows if a woman is at greater risk of having a baby with Down's syndrome or neural tube defects.

If a woman tests positive, further evaluation is needed. In fact, a large number of women who test positive on this screening are sent for further procedures. These are the amniocentesis and chorionic villi sampling. These are invasive procedures that carry a risk of miscarriage or damage to the baby. This new blood test offers an alternative to these invasive procedures.

The blood test works by looking for fragments of the baby's DNA in the mother's blood. Babies with Down's syndrome have an extra chromosome on pairing number 21, so the disorder is known as trisomy 21. This genetic information can be found in the DNA floating in mom's blood stream. The test appears to work for identifying other disorders involving an uneven number of chromosomes, such as Edward syndrome and Patau syndrome.

For the original study, the researchers used blood samples from women pregnant with babies with one of these disorders, usually Down's syndrome and women with normal pregnancies. In all cases, the researchers were able to correctly identify the babies with the chromosomal abnormalities using only blood samples from the mother.

In addition to reducing the risks associated with invasive procedures, this test may offer information earlier in the pregnancy. The fetus's DNA is present in the mother's blood stream earlier in the pregnancy than the time when CVS and amniocentesis are performed. This would allow women to have this information earlier in the pregnancy without risking miscarriage.

This blood test will likely not be available for a few years. Further studies are being done to prove the effectiveness of the test. Once the large scale studies are completed, the test will move through the approval process and then be made available to women.

Related Articles:

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Prenatal Testing: Amniocentesis

Testing in Pregnancy

Learn more about Pattie Hughes

Pattie Hughes is a freelance writer and mother of four young children. She and her husband have been married since 1992. Pattie holds a degree in Elementary Education from Florida Atlantic University.

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