Foetal DNA testing – a safer way to test unborns for genetic diseases.

With the identification of foetal DNA in a mother’s blood scientists from the Chinese University of Hong have proposed a technique which may lead to a non-invasive and safer way of testing unborn babies for genetic diseases.

The study appeared in Proceedings of the National Academy of Sciences Prof Dennis Lo, of the Chinese University of Hong Kong, and colleagues reported the study in the Proceedings of the National Academy of Sciences on 4^th October 2005.

Currently, pregnant women can be given amniocentesis, carried out at 15 to 18 weeks' gestation, which involves using a needle to collect fluid from the amniotic sac surrounding the foetus. However the test causes a miscarriage in around one in 100 cases. Another one of the tests available is chorionic villus testing. This involves taking a small sample the mat of chorionic villi, or finger-like projections on the foetal side of the placental tissue at 10 to 12 weeks but it too carries a risk of miscarriage in up to one per cent of cases. Hence scientists are basically trying to find ways of bettering these existing pre-natal tests, which carry a risk of miscarriage.

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It has been known for more than three decades that a low concentration of foetal DNA is present in the blood plasma of pregnant women but locating it has always intrigued scientists and thus limited its clinical usefulness.

The team at the Chinese University was investigating if there were differences between the chemical behaviour of foetal and maternal DNA. It is then that they found that methylation (type of chemical modification), occurs at much higher levels on a gene called maspin in maternal DNA than foetal DNA. Unmethylated foetal DNA was detected in maternal blood plasma throughout pregnancy, but disappeared within 24 hours of delivery, indicating it is specific to pregnancy.

The results show that it is possible to find universal epigenetic markers for foetal DNA in maternal blood and may provide the basis for developing novel, non-invasive methods for prenatal diagnosis and foetal monitoring. "We believe that this study represents a significant step forward," said Prof Lo.

The team led by Dr Stephen Chim said they had shown it was possible to find genetic markers for foetal DNA in maternal blood. According to them this could therefore provide the basis of new non-invasive ways of diagnosing conditions in foetuses, and monitoring development throughout pregnancy. "We believe this marks a significant step forward," the researchers said.

Dr David Liu, director of the foetal care unit at City Hospital in Nottingham, has also been working on ways of identifying foetal cells in the mother's blood. He told the BBC News website: "The team in Hong Kong has found a way of picking out what is baby and what is mother, by looking at a molecular biology level. The next step is how this works in the clinical arena. Although cells can be picked out, the researchers need to find out whether it will be applicable for testing for the various conditions we are looking at." Dr Liu added: "The tests we have at the moment are invasive, and carry a risk of miscarriage. "Obviously, if we can avoid that, it would be better."  

Inspite of the benefits, as judged by the investigating scientists this technique seems to raise quite some concern regarding how this new technology may be used.
A spokesman for the charity Life expressed his views: "Prenatal genetic testing has proved to be a decidedly mixed blessing, and is increasingly being used to promote an unabashedly eugenic agenda, involving the arbitrary destruction of any life seen as imperfect or burdensome on the rest of society. Already 96% of unborn children diagnosed with Down's syndrome are aborted in the womb, while abortions are routinely carried out for relatively minor impairments such as club foot and cleft palate. Once life was seen as inviolable for its own sake: now our ethic of life is consumer-led, based on utilitarian notions of usefulness and convenience."

This foetal DNA testing, though simple and easy may raise ethical questions. Some researchers worry that gender tests like this will lead to abortions when parents want a baby of a given sex. The skepticism is also regarding the worry that if foetal DNA testing can one day routinely show whether an early foetus has genes that predispose it to cancer or other diseases, parents-to-be could face very difficult decisions.