Breakthrough as 'safe' blood test screens unborn babies for disease

HOPE: Discovery will cut risk of miscarriage

Mark Henderson

A blood test for pregnant women that could detect virtually any genetic disorder in an unborn child without risking a miscarriage has been developed by scientists.

The experimental technique promises to transform prenatal testing for inherited diseases, by identifying conditions such as cystic fibrosis and sickle-cell anaemia from traces of a foetus's DNA in its mother's bloodstream.

If encouraging preliminary research is confirmed by larger trials, the safe and non-invasive procedure could replace diagnostic techniques such as amniocentesis.

These involve inserting a needle in the womb, and cause miscarriage in about 1 in 100 pregnancies.

The test could potentially be performed in the eighth week of pregnancy, up to seven weeks earlier than existing procedures.

Abortions

It also raises the prospect of more extensive prenatal screening for inherited disease, which is currently offered only to high-risk couples because of the danger of miscarriage.

This, however, would be ethically contentious as it would be likely to lead to more abortions as more inherited diseases were detected early in pregnancy.

Dennis Lo, of the Chinese University of Hong Kong, who led the team that developed the non-invasive prenatal diagnosis (NIPD) test, said that it could eliminate the dangers of amniocentesis completely.

"Up until now, testing of foetal DNA for most genetic conditions has required sampling foetal tissue, which is invasive and carries a 1pc risk of losing the baby," he said.

"This means that deciding whether to test is a big psychological burden.

"The promise of our technique is that it doesn't have that risk. It is safe for the baby, and psychologically easier for the mother."

At about f150,000, the new test is currently too expensive for routine use and it still needs to be clinically validated. Professor Lo expects the cost to fall below f1,190 within five years, by which time it should be approved and widely available.

Independent scientists welcomed the advance but cautioned that the test had so far been performed only once and much more work was needed to confirm that it was as accurate as amniocentesis..

Lyn Chitty, Professor of Genetic and Foetal Medicine at the Institute of Child Health in London, said: "It is set to change obstetric practice and make prenatal diagnosis much safer.

"But we do need to do a lot of work both on laboratory evaluation and educating the public."

hnews@herald.ie