TORONTO - Babies born even just a few weeks prematurely face a number of potential long-term health problems, a new study warns.

The study found that babies born between 34 and 36 weeks gestation were more than three times as likely to have cerebral palsy as full-term babies and were also at increased risk of having developmental delays or being mentally handicapped.

The absolute risks were not enormous - 2.1 per cent of the late pre-term babies in the study had one of the developmental problems the researchers looked for, compared to a rate of 1.2 per cent in babies born at term.

And while the lead author said there is no need for parents to panic, she did suggest they and their doctors should remember that late pre-term babies need to be watched for signs of health problems.

"While these rates are low, the fact is that pre-term babies are quite often treated as though they're full-term babies," said Joann Petrini, an expert in prematurity and director of the perinatal data centre at the U.S. national office of the March of Dimes, a charity devoted to preventing birth defects and infant mortality.

"I mean, they look chubby many times. They look healthy and many times are not and are discharged and may not get the attention that a pre-term baby needs."

The study, published Thursday in the Journal of Pediatrics, compared rates of cerebral palsy, developmental delay or mental handicap and seizures in over 140,000 babies born at 30 weeks gestation or higher in northern California from Jan. 1, 2000 to June, 30, 2004.

The babies were born to parents who had health-care coverage through the Kaiser Permanente medical care program. The fact that the parents were affluent enough to have this health insurance coverage suggests the results may be conservative, Petrini admitted. Rates might have been higher if the study group also included children born to parents without health-care coverage or living in poorer parts of the United States.

It is well established that babies born very prematurely face myriad health hurdles throughout their lives. But not as much research has been done to document what faces children born a few weeks before full term, who make up a growing segment of the baby population.

In 1990, late pre-term births made up 7.3 per cent of all live births in the U.S. In 2005, that figure had risen to 9.1 per cent.

The increased use of assisted reproductive techniques has led to an epidemic of multiple births; women carrying twins or higher order multiples are much more likely to give birth before their fetuses reach full term. The trend towards having babies later in life is also contributing to the increase in pre-term births.

As well, technical advances - in the ability to monitor fetuses in the womb and care for premature babies after birth - may be leading obstetricians and neonatologists to think of late pre-term birth as virtually risk free, Dr. Michael Kramer of McGill University wrote in an editorial that accompanied the article.

"I think it's important for the mothers and families and doctors to be aware of them (the risks) because with increasing technology of following fetuses and more and more inductions and more and more caesareans, we need to know whether the benefits of these procedures . . . exceed the harms," he said.

Kramer, who was not involved in the study, is a pediatrician and serves as scientific director of the Institute of Human Development, Child and Youth Health, one of the Canadian Institutes of Health Research.

He said that while some late pre-term births are unavoidable and others are medically essential, in some cases it is a judgment call as to whether a woman should be allowed to try to reach full term or should be induced.

When those decisions are being made, it's important that the possible health risks facing late pre-term babies be added to the mix of factors being weighed, he said.

"At some point, with increasing technology and increasing intervention, we're going to be doing more harm than good. I'm not saying we're there yet. But we need to keep an eye on this."