No Accuracy in Genetic Screening of Unborn Babies

A scientist has warned that new tests for genetic screening of unborn babies will not be 100 per cent accurate and may scare parents. Lord Robert Winston has made the comment in the wake of a recent study, in which researchers claimed that they could predict the whole genetic code of a foetus by taking a blood sample from a woman who was 18 weeks pregnant, and a swab of saliva from the father.

The researchers had said that with the help of the study, scientists could soon be able to routinely screen unborn babies for thousands of genetic conditions, raising concerns the breakthrough could lead to more abortions, the Telegraph reported.

They believe that, in time, the test will become widely available, enabling doctors to screen unborn babies for some 3,500 genetic disorders.

Now some British experts have cautioned that the test may do more harm than good because in many cases it would be very hard to predict how a mutation would affect a child and how severe their disability might be.

At the moment the only genetic disorder routinely tested for on the NHS is Down's syndrome.

This is a large-scale genetic defect caused by having an extra copy of a bundle of DNA, called a chromosome.

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Other such faults are sometimes tested for, but usually only when there is a risk of inheriting them from a parent.

By contrast, the scientists say their new test would identify far more conditions, caused by genetic errors.

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However, they warned it raised "many ethical questions" because the results could be used as a basis for abortion.

These concerns were amplified by pro-life campaigners, who said widespread use of such a test would "inevitably lead to more abortions".

The American scientists were able to map the baby's genetic code principally from tiny traces free-floating DNA, which makes its way into the mother's blood.

Blood sample DNA from the mother was also studied as well as DNA extracted from the father's saliva.

Fitting pieces of the genetic jigsaw together, scientists in the US were able to reconstruct the entire genetic code of an unborn baby boy.

They were then able to see what spontaneous genetic mutations had arisen.

Such natural mutations, called 'de novo' mutations, are responsible for the majority of genetic defects.

By checking their prediction of the baby's genetic code with actual DNA taken after the birth, the team from the University of Washington in Seattle, found they were able to identify 39 of 44 such mutations in the child.

De novo mutations are thought to play a role in a number of complex conditions such as autism and schizophrenia.

The team also tested their approach on a woman who was earlier in her pregnancy than 18 weeks, and found it still worked.

"This work opens up the possibility that we will be able to scan the whole genome of the foetus for more than 3,000 single-gene disorders through a single, non-invasive test," Dr Jay Shendure, the lead scientist, said.

The study has been published in the journal Science Translational Medicine.

Source-ANI