By Richard Alleyne

The entire DNA profile of an unborn child has been mapped from the blood of its mother for the first time in a breakthrough that could allow parents to safely check for a host of genetic and inherited disorders.

Researchers hope it will provide a better and risk-free alternative to the current invasive tests which increase the chance of the mother suffering a miscarriage.

However it also raises ethical concerns that it could eventually be used to select “designer babies” and screen out offspring with less serious abnormalities.

At the moment the only way to scan for genetic defects in the womb is to carry out operations which involve scraping away a sample of cells from the placenta (chorionic villus sampling) or removing – via an injection – fluid from the womb (amniocentesis).

Both involve a one per cent risk of triggering a miscarriage or infection and so are only carried out if the probability of a defect is high.

The new test, which is published the journal Science Translational Medicine, works by separating the babies DNA from the blood of the mother.

It has long been known that during pregnancy around 10 per cent of the mother’s blood plasma contains the DNA of the unborn child.

Scientists have been working hard to screen it for obvious diseases such as Down’s Syndrome but the new research takes the whole process a step further.

Dr Dennis Lo, the Chinese University of Hong Kong, and his team have used new technology to separate the DNA from the mother’s and then map its entire genetic profile.

The technological breakthrough, which at the moment is very expensive, means that a whole host of genetic disorders can be screened for.

Eventually as genetic research improves it could also be used to obtain information on the risk of your child developing other diseases such as cancer and heart disease later in life.

“This information is importqnt because it demonstrates that a non-invasive genome wide scan of the foetal genome from maternal plasma is possible.

“The non-invasive nature of our approach makes it safer than conventional procedures that require invasive sampling.

“However the new approach also raises a number of ethical, legal and social issues that require active discussion among clinicians, scientists, ethicists and the community.”

In the study, the researchers recruited a couple undergoing prenatal checks for an inherited blood disease called beta-thalassemia which causes anaemia.

They first mapped the DNA of both the mother and the father and then took a blood sample from the pregnant woman.

Within the four billion DNA molecules sequenced in the sample, they separated the foetal DNA strands that were buried deep within it.

The researchers were able to piece together a genome-wide genetic map of the foetus from the plasma sequencing data.

Finally, they scanned the genetic map for genetic disorders and found that the baby had inherited the beta-thalassemia mutation from the father.

In other words, the foetus was a carrier of the disease.

The scientists hope that the same technique will detect other abnormalities in an unborn child’s DNA such as Down’s, which cuases learning difficulties, Edwards’ syndrome, which causes structural malformations in the foetus, and Patau’s syndrome, which can result in severe physical and mental impairment.

It could also eventually be used to screen for muscular dystrophy and haemophilia.

Professor Donald Peebles, spokesman for the Royal College of Obstetricians and Gynaecologists, said: “This is an important step towards making a safe, pre-natal diagnosis a possibility.”

Dr Caroline Wright, Head of Science, at the Public Health Genomics Foundation, said it was a pioneering study.

Alastair Kent, Director, Genetic Alliance, said it was an “exciting development”.

“This offers hope to couples at risk of having a baby affected by a life limiting genetic disease.

Full article


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