Hope for non-invasive pregnancy test
Dr. Kirsty Horsey
Progress Educational Trust
07 March 2004
US researchers have developed a new method for testing fetal DNA, which does not involve the use of invasive techniques such as amniocentesis or chorionic villus sampling (CVS). The scientists, based at the biotech company Ravgen, have found a way to increase the amount of fetal DNA that can be extracted directly from the mother's blood. A commentary piece accompanying the study, which appears in the Journal of the American Medical Association (JAMA), says that the work could have 'profound clinical implications' for prenatal diagnosis and cancer screening.
Currently, tests for Down syndrome and genetic conditions such as cystic fibrosis rely on taking fetal cell samples, using either amniocentesis or CVS. Both techniques involve injecting a needle into the womb, and so carry a small risk of miscarriage. Because of this, researchers have been trying for some time to develop a non-invasive technique for carrying out genetic tests during pregnancy.
It was already known that a small number of cells from the fetus always find their way into the mother's bloodstream, where they are attacked by the maternal immune system. But although previous studies have shown that small amounts of the resulting 'free fetal DNA' can be detected in a sample of the mother's blood, it is usually swamped by large amounts of DNA from maternal white blood cells.
In the new study, the researchers treated blood samples from pregnant women with the chemical formaldehyde, which 'hardened' the maternal blood cells, stopping them from bursting and releasing their DNA. This boosted the relative amount of fetal DNA present, from around 7 per cent in the untreated samples to an average of 25 per cent in a follow-up study of 69 formaldehyde-treated samples. Over a quarter of the samples contained 50 per cent fetal DNA, prompting the authors to write that 'this lays a solid foundation for the development of a non-invasive prenatal diagnostic test'. The JAMA commentary piece adds that as well as prenatal tests, the technique could also potentially be used to detect cancer cells, and monitor their spread.
Alastair Kent, director of the UK's Genetic Interest Group, told BBC News Online that a non-invasive prenatal diagnosis technique would give pregnant women the opportunity to have information on which they could make decisions, 'without potentially putting the future of a healthy pregnancy at risk'.
© Copyright Progress Educational Trust
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.
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