Babies born more than five weeks prematurely could be much more likely to suffer brain damage that leads to behavioural and educational problems in adolescence, a study suggests.

The report's authors were quick to point out that their findings were by no means conclusive, but called on doctors to take steps to reduce the likelihood of brain abnormalities in such children.

While their impaired reading skills in their study group may be down to social factors, behavioural problems were strongly linked with abnormal brain scans, they said.

The findings are published in The Lancet medical journal.

Brain damage

The study, led by a group of doctors at University College London, started in 1979 and looked at babies who were among the first to have ultrasound brain scans.

The subjects' brains were scanned for abnormalities

The babies chosen to take part were born after less than 33 weeks of pregnancy.

They had check-ups at intervals until they were 14 or 15, when they were given a series of reading, spelling and behavioural tests.

The results of these were compared with the results of magnetic resonance imaging (MRI) brain scans.

The overall findings were compared with those of other 14- to 15-year-olds who were born after a full-term pregnancy.

Abnormalities

Of the 72 children who had been born prematurely, 40 had abnormal MRI scans. This compared to one abnormal scan out of the 21 children born after a full-term pregnancy.

Another 15 adolescents in the premature group had scans showing slight abnormalities, compared with five in the control group, but the significance of the abnormalities was uncertain.

The most common abnormality among those who had been born prematurely was in the part of the brain called the white matter, which is involved in carrying signals between different areas of the brain and between the brain and spinal cord.

The adolescents with abnormal scans were much more likely to have behavioural problems, such as difficulties at school, and all the adolescents with abnormal MRI scans in the premature group had lower reading scores.

'Excess of problems'

"Individuals born very pre-term show an excess of neurocognitive and behavioural problems in adolescence," the researchers said.

They stressed that due to the small size of the study group, parents should not get overly concerned if they gave birth to a premature baby.

But they concluded: "If the prognosis of very pre-term infants is to be improved, structural brain abnormalities must be prevented or, at least, the prevalence reduced."