Babies born very prematurely are far more likely to die in childhood, and significantly less likely to have children themselves, a study has found.

Using data from more than a million births in Norway between 1967 and 1988, an international team discovered that babies born at between 22 and 27 weeks of gestation are much more likely to die in childhood.

Boys are five times more likely to die in early childhood, and seven times more likely to die in later childhood, than are boys born after the normal gestation period. Girls are almost ten times more likely to die as infants, but have no increased risk if they survive infancy.

Boys born between 28 and 32 weeks gestation also suffer about 2½ times a greater risk of death, but girls do not, the study found.

Premature birth also affected the children’s chances of becoming parents themselves, the team lead by Geeta Swamy, of Duke University in Durham, North Carolina, said.

Those born extremely prematurely – at 22 to 27 weeks – are only a quarter to a third as likely to become parents as babies of normal gestation. The effect is still detectable in those born between 28 and 32 weeks, but is much smaller, with a roughly 20-30 per cent reduced chance.

Improving treatments mean that many more very premature babies are surviving than in the past. But many studies have shown that the risks of disability are increased.

The Norwegian data, published in Journal of the American Medical Association, covers 1.16 million births, followed up until 2002. The study also found that preterm babies do less well at school. The most premature girls are about 30 per cent less likely to complete school, and 14 per cent less likely to get a degree.

Among boys, the most premature are 40 per cent less likely to complete school, and 30 per cent less likely to get a degree.

The same applies, on a diminishing scale, to those born at 28-32 weeks and at 33-36 weeks of gestation.

The study covers a period in which obstetric care was not as good as it is now, so it is possible that these handicaps would now be smaller.

Despite the findings, the majority of premature babies have good health, two American doctors said in an editorial in the journal. Clinicians, they said, can extend “guarded optimism” to the families of children who are born very premature.

But because the lifetime risk of poor health is increased in these children, parents should make sure that their doctors are informed that they were born early. There were 550 babies born at less than 24 weeks’ gestation in Britain in 2005-06, and another 3,600 at 24-28 weeks. There were 14,900 births between 29 and 34 weeks. All these babies are at risk potentially of some of the problems identified in the study.