TUESDAY, Sept. 2 (HealthDay News) -- A study looking at children born extremely prematurely (at or before 25 weeks of gestation) finds they are at significantly higher risk for behavior problems by age 6, with boys particularly vulnerable.

"Attention problems and social problems with peers have been reported previously" in children born prematurely, noted study lead author Dieter Wolke, professor of developmental psychology and individual differences at the University of Warwick in the United Kingdom.

But the study, which compared parent and teacher reports of behavior problems at age 6 in 200 children born preterm against 148 children who were born full-term, is more comprehensive, he said, and draws from more than one center. "Most previous studies have used parent reports, very few teacher reports," Wolke said, while his study used both. "Parent reports can be biased," he noted.

The new findings were published in the September issue of the journal Pediatrics.

In the study, teachers and parents were asked about emotional problems, conduct, hyperactivity, peer problems, social behavior and adaptability to school.

Overall, 19.4 percent of the extremely preterm children had behavior problems, but just 3.4 percent of the control children did. "We found that already in 6-year-olds, the extremely preterm child had four times more often emotional problems (anxiety, depression) than controls," Wolke said. "This has not been reported for larger preterm [born after 25 weeks but not full term] children."

Boys were twice as likely as girls to suffer behavioral problems, the researchers found. When they assessed children's cognitive functioning, it explained the hyperactivity and conduct problems, but problems such as poor attention, poor peer relations and emotional problems couldn't be explained by cognitive function, Wolke said.

So what's at the root of the difficulties? It's not known for sure, Wolke said. But he suspects they are due to "altered brain development from white to grey matter that takes place between 24 to 27 weeks' gestation."

The study is a landmark one, noted Dr. K.J.S. Anand, an attending physician at Arkansas Children's Hospital and a professor at the University of Arkansas for Medical Sciences, Little Rock. He has also done much research on the topic.

With his colleagues, Anand has proposed a possible mechanism, saying the problems may be the result of the maternal separation experienced by these extremely premature infants, impacting the developing brain.

Because some children were lost to follow-up, Anand said, "it is likely that their results may even underestimate the true prevalence of these problems in society."

While Wolke said the problems are child-driven, a result of brain development, and that parents as such can't do much, Anand suggested that greater contact between parents and babies during the first days after delivery may help.

More information

To learn more about preterm birth, visit the March of Dimes.