January 12, 2011

DNA Test Reveals Down’s Syndrome

Research published on Tuesday states that DNA in a pregnant woman's blood can reliably show whether her fetus has Down's syndrome, which can reduce the need for invasive testing procedures like amniocentesis.

Down's syndrome, a major developmental disorder also known as trisomy 21, occurs in around one in every 800 live births.

Pre-natal diagnosis mainly entails sampling fluid from the amniotic sac enveloping the fetus.  Another technique is called chorionic villus sampling, and it entails taking a sample of placenta.

Both techniques carry a one-percent risk of miscarriage, which is why they are reserved for older mothers-to-be and other women deemed at risk.

Researchers led by Dennis Lo, a professor at the Chinese University of Hong Kong, carried out the first large-scale investigation into new DNA technology which sequences telltale fetal molecules in maternal blood.

The test was carried out among 753 mothers who were all in the high-risk category.

Eighty-six of the women were found to be carrying a fetus with Down's.  The test detected this with 96.6 percent accuracy and did not deliver any "false negatives," which means that it wrongly said a woman did not have a Down's fetus.

"The sequencing test could be used to rule out trisomy 21 among high-risk pregnancies before proceeding to invasive diagnostic testing," says the study, published online by the British Medical Journal (BMJ).


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