The discovery will allow them to monitor development using a special type of brain scan, known as functional magnetic resonance imaging.

In the past, doctors were only able to judge development indirectly by looking for physical movement in response to stimulation.

But using a new technique they were able to detect a striking increase in brain activity, when music was played to babies in the womb.

Activity

In a study to develop the technique, three pregnant women were given a scan.

Beforehand, they were asked to record a nursery rhyme. This was played down a tube to near the mother's abdomen for 15 seconds, followed by 15 seconds silence.

The recording was played in this way 18 times, during which the babies' brain activity was measured - the increase in activity was noted in two of the three babies.

The study was performed by researchers at Nottingham University and details of its progress were published in The Lancet medical journal.

Dr Penny Gowland, a physics lecturer at the university, told BBC News Online it was the first time an unborn child's brain activity had been directly observed.

"So far all we've done is shown that we're able to do it," she said.

However, since the paper was sent to the Lancet, she said, the team had tested the technique on more babies and had a similar success rate.

Monitoring development

"What we want to go on to do is to study normal brain development, and set a baseline for what normal brain activity is in the foetus."

This would include looking at how babies develop habits while they are in the womb.

"You know how some people say their baby always kicks when the music for Eastenders comes on? Well we want to see whether the baby responds the same after hearing the music for a week or differently.

"Ultimately we're interested in seeing what happens in compromised pregnancies - pregnancies where the baby's not growing properly."

Usually the brain is protected so it grows normally and the body suffers. But in severe cases the brain can be affected, and this is thought to account for 60% to 90% of cases of cerebral palsy.

"So we're interested in seeing how the brain function is altered in these compromised pregnancies - anatomically and functionally now," Dr Gowland said.

Legal importance

This information could prove of the utmost importance in future, as a number of High Court cases have revolved on the question of whether hospital staff were responsible for a child suffering cerebral palsy.

One recent case produced a damages payout of �2.35m.