Risk Free Test for Downs


Every healthy baby has twenty-three pairs of chromosomes in each cell. Just one less or one more and the fetus ends up with a genetic defect. Children with Downs Syndrome have an extra copy or trisomy of chromosome twenty-one. Today most expectant moms are offered genetic testing, with some screening for Down's.

Several tests can indicate a problem with the baby, but to be certain, doctors must perform invasive tests which carry the risk of miscarriage. It requires the insertion of a needle into the uterus to extract fluid surrounding the fetus for testing.

Now a new method undergoing trials is not only effective but risk-free since all it needs is the mother's blood. It analyzes fragments of fetal DNA floating in her blood. These DNA fragments, free of a cell, can be isolated from the plasma portion of the mother's blood. The test involves sequencing millions of DNA fragments to detect extra copies and it only takes a few days.

When researchers screened about a thousand expectant moms at ten weeks, there were fewer false positives compared to other noninvasive tests such as ultrasound and a hormone-based blood test. While the test result is not a certainty as you would expect with an amniocentesis, in trials it was ninety percent accurate in women who are more likely to have a downs baby.

In addition to Downs Syndrome, the test can also detect other similar genetic abnormalities such as Edwards syndrome involving trisomy of chromosome eighteen and Patau syndrome which is caused by trisomy of chromosome thirteen. Having this additional noninvasive test available to all expectant moms would offer them greater peace of mind through their pregnancy.

More Information

Down Syndrome
Comprehensive information on Down Syndrome from MedLine Plus, a service of the U.S. National Library of Medicine, National Institutes of Health

Down's pregnancy blood test on trial
"A simple blood test during pregnancy which can detect Down's syndrome in the developing foetus is to be trialled by the NHS."

Non-invasive first trimester blood test reliably detects Down's syndrome and other genetic fetal abnormalities
"New research has found that routine screening using a non-invasive test that analyzes fetal DNA in a pregnant woman's blood can accurately detect Down's syndrome and other genetic fetal abnormalities in the first trimester. The results suggest that the test is superior to currently available screening strategies and could reshape standards in prenatal testing."