March 7, 2011
Down Syndrome Can Be Diagnosed With Blood Test
Researchers from Cyprus report that a simple blood test can predict whether a baby is likely to have Down Syndrome.
DNA differences between the mother and the fetus can be shown to accurately predict which fetuses are at risk of developing the syndrome, Reuters reports.
Down Syndrome occurs in 1 in 700 live births and is the most common genetic cause of mental retardation. The risk of having a baby with Down Syndrome occurs when a child has three copies of chromosome 21 instead of the normal two. The risk increases as women get older. The risk for a 40-year-old mother is 16 times that for one who is 25.
Amniocentesis is the current test that is performed to find if a baby is likely to be born with Down Syndrome. This test is generally done at about 15 or 16 weeks gestation and involves taking amniotic fluid from the mother by inserting a hollow needle into the uterus.
This test also carries a small risk of spontaneous miscarriage, generally 1 to 2 percent, and scientists have been looking for new less invasive ways to test for Down Syndrome and other genetic issues. Patsalis calls the results "very exciting" but said the test needs to be trialed in a larger study of about 1,000 pregnancies and could lead to changes in clinical practice within the next few years.
Patsalis' method examines differences in the DNA methylation patterns, which control levels of genes between mother and fetus. The test involves taking a small amount of blood from the mother when she is between the 11th and 13th week of her pregnancy to detect extra copies of chromosome 21 in the fetus.
In the initial, small trial of 40 pregnant women, researchers were able to correctly diagnose 14 cases of extra copies of the chromosome, and 26 normal fetuses, highlighting its clinical potential. "Such a non-invasive approach will avoid the risk of miscarriages of normal pregnancies caused by current, more invasive procedures," researchers conclude in their findings, published in a recent issue of Nature Medicine.
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