Blood Test Determines Genetic Risks in Fetus

Free fetal DNA (ffDNA) is present in maternal blood from early in gestation (six weeks) and its use for prenatal diagnosis could avoid invasive testing, with considerable benefit to parents, many of whom will already have had an affected pregnancy.

Dr. Lyn Chitty, a reader in genetics and fetal medicine at the Institute of Child Health, University College London (London, UK), said, "The advantages of this test are clear when used in women at high risk of a genetic disorder. It allows for earlier determination of fetal sex than was previously possible using either chorionic villus sampling or ultrasound. It avoids the risks associated with invasive testing in about half of the women.”

The test involves tiny amounts of ffDNA that make up 5% of a mother's DNA in her blood during early pregnancy. This ffDNA is analyzed to identify genes that are present in the father and can be passed on to the fetus. Dr. Chitty, who described the test at the September 2006 annual meeting of the British Society of Human Genetics in York (UK), observed that a non-invasive test for cystic fibrosis could probably be developed within five years. In addition, other scientists are using the technique to develop a test for Down's syndrome, which they say could be available within three to five years.



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Institute of Child Health, University College London