'Safer' test for Down's developed

Scientists say they have developed a safer blood test that can tell women if their unborn baby has Down's syndrome. Invasive procedures currently used risk miscarriage and damage to the foetus. A Stanford University test of DNA evidence in 18 pregnant women's blood correctly identified nine cases of Down's syndrome, reports PNAS journal. The university now wants a larger-scale test. Babies with Down's syndrome have an extra copy of chromosome 21, causing physical and intellectual impairments. If a foetus has three copies of chromosome 21 rather than the normal two, there will also be a relative increase in the quantity of chromosome 21 in the mother's blood because DNA can cross the placenta from the baby to the mother. The "shotgun sequencing test" identifies and counts these fragments of DNA and is sensitive enough to... [read full story]