Hundreds of unborn babies afflicted with a common but often fatal foetal abnormality may be saved by a pioneering keyhole surgery technique in the womb, according to research published today.

Hundreds of unborn babies afflicted with a common but often fatal foetal abnormality may be saved by a pioneering keyhole surgery technique in the womb, according to research published today.

Doctors have discovered an new method of treating babies in the womb unable to develop their lungs because of the liver herniating into the chest. This abnormality affects one in 3,000 babies, but it may be fatal for about half of the babies born with the condition.

Using keyhole surgery, a balloon is inserted into the main airway of the unborn baby during the 26th week of pregnancy. It is removed during the 35th week. The balloon stops organs moving into the chest area, enabling the lungs to develop fully.

Results from tests showed that among the 50 per cent of babies for whom the condition was likely to be fatal, the procedure boosted the survival rate from 8 per cent to more than 60 per cent.

The study, to be published today in the journal Ultrasound in Obstetrics & Gynaecology, consisted of 30 pioneering balloon operations over two and a half years as part of a collaboration between King's College Hospital in London, Leuven University in Belgium and the University of Barcelona.

Professor Kypros Nicolaides, of King's College Hospital, who was behind the research, said: "It is a common foetal abnormality and it can happen to anybody. The membrane that forms between the chest and the abdomen, the diaphragm, may fail to close completely, which can lead to the stomach, gut and liver moving into the chest area.

"This results in underdeveloped lungs. Half of all babies can survive, the other half do not and the majority of parents normally decide to terminate the pregnancy.

"We focused on the half that do not and found that when we refined the procedure, the survival rate was 65 per cent."

During the study, scientists slowly refined the technique, replacing general with local anaesthetic and modifying the balloon-removal procedures.

"The key to the procedure is the fact that we are not only expanding the lungs, but we are also making them grow during pregnancy," said Professor Nicolaides.

Professor Stuart Campbell, former head of obstetrics at King's College Hospital and St George's hospital and editor of the journal, said that the procedure could potentially alleviate the trauma of hundreds of parents whose unborn babies suffer from such conditions.

Professor Campbell said: "This relatively common abnormality can be devastating to parents who until now could be offered little hope that their babies would survive."

"With the help of better scanning techniques, we can accurately diagnose most foetal anomalies and we are now moving into the next phase where some abnormalities can be successfully treated in the womb."