TUESDAY, Nov. 23 (HealthDay News) -- Being born just a few weeks early might have a long-term impact on a child's IQ and ability to pay attention, new research suggests.

In a study that compared babies born at term (40 weeks) to those born between 34 to 36 weeks (called "late pre-term"), researchers found that the children born early had more than twice the risk of having an IQ score below 85 and about double the risk of having socioemotional difficulties, such as attention problems, at age 6.

"There's a subgroup of children born late pre-term that have an increased risk of developing problems by age 6," concluded study author Nicole Talge, a postdoctoral research associate in the department of epidemiology at Michigan State University in East Lansing, Mich.

"What this study tells us is that late prematurity is not a benign situation. Not every kid will have a problem, but there's a higher chance for some to have interaction problems, attention problems and lower IQ," added one expert, neonatal psychologist Cheryl Milford of Magee-Women's Hospital at the University of Pittsburgh Medical Center.

Milford said the reason for the risk is that the brain simply isn't developed enough at 34 to 36 weeks. "A lot of the development of higher-order functioning in the brain is occurring in the 34-to-36-week range," she explained, adding that "there's a reason that humans gestate for 40 weeks."

The current study included 168 pairs of babies -- one born at term and one born between 34 and 36 weeks. The babies were born during 1983 and 1985. At age 6, they had their IQ scores measured and their teachers reported on classroom behaviors.

The Michigan team found that late pre-term birth more than doubled the risk of having an IQ score of less than 85. Furthermore, the odds of having emotional difficulties, such as attention problems, were about twice as high for those born a little bit early compared to the children born at full-term.

Results of the study appear in the December issue of Pediatrics.

Talge said it's important to note that not every child born at 34 to 36 weeks had problems. In fact, most didn't. "Only about 20 percent fell below that IQ threshold, and that means 80 percent were above that. And, about 20 to 30 percent had internalizing or attention problems," she said.

"We now have a greater understanding that each week matters," said Dr. Michael Msall, chief of developmental and behavioral pediatrics at the University of Chicago Medical Center. However, he sad that "the good news from this study is that at age 6, even in a different era of neonatology [the 1980s], these kids did quite well. Yes, on a population basis, there may have been some problems, but I think that it may be like being five pounds overweight on a population basis, and most of these differences may be subtle."

However, he said that if parents see that their child is struggling with schoolwork, or is having a hard time paying attention in school, they shouldn't hesitate to ask for help. "Talk to your child's pediatrician or their teacher; let them know you want to make sure your child stays on track. Recognize the problems and develop a strategy to manage them," said Msall.

Milford agreed. "Babies who are born late pre-term look like small, full-term babies, and for a long time the perception was that they were just a little early, but that they were mostly developed," she said. "The reality is, if you had a late pre-term infant, you should be looking to see if they're on track. Do they have any behavioral issues? If so, you need to find out what resources are available to you in the community and at school."

More information

Learn more about premature birth and what you can do to help prevent it from the March of Dimes.