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Preemie Growth Study Finds a Few Surprises

They struggle in school but stay out of trouble, says long-running study

WEDNESDAY, Jan. 16, 2002 (HealthDayNews) -- Despite marked educational setbacks in early adulthood, people who were born extremely underweight don't seem prone to the behavior problems that typically accompany such learning difficulties, a new study says.

Previous research had shown that infants born weighing less than about 3.3 pounds struggle in school as youngsters and have lower IQs than heavier infants do. The new findings, show those troubles haunt them through the teen years and into early adulthood. The researchers tracked the infants for 20 years.

However, the researchers say, as they mature, former featherweight infants aren't more likely than their peers to run into trouble with the police, use illegal drugs or become pregnant as teens -- problems experts had feared would befall them.

"The behavior issue is really surprising," says Dr. Marie McCormick, a Harvard pediatrician and co-author of an editorial accompanying the journal article, which appears in tomorrow's issue of the New England Journal of Medicine. "This is a very intriguing result, and really needs to be explored further."

Low birth weight has become more common as the rate of premature delivery has climbed, thanks in large part to greater use of fertility treatments that promote multiple pregnancies. At the same time, doctors have become increasingly adept at keeping even the slightest infants alive on respirators. However, it comes with a trade-off: impaired lung function can lead to varying levels of brain damage.

Roughly 1 percent of preemies are considered extremely underweight. Many of these children show signs of significant cognitive trouble in elementary school, including poor academic performance and learning disabilities.

In earlier research, Maureen Hack of Case Western Reserve University in Cleveland reported as much in a group of Ohio youngsters born in the late 1970s.

This time, Hack and her colleagues extended their observations for another decade. They compared the academic and social progress of 242 of these infants with that of 233 normal-weight babies raised in similar communities and circumstances in Cleveland. Because they controlled for social and economic differences, the gaps in academic success weren't due to poverty, a major indicator of poor educational advancement.

Not surprisingly, people in the once-undersized group continued to struggle academically. They had lower average IQs -- 87 versus 92 -- and scored worse than their peers on general tests of academic achievement. However, the researchers did not measure maternal IQ, which strongly predicts a person's intellectual capacity.

Men, but not women, were somewhat less likely to have graduated high school, much less likely to be enrolled in a post-secondary school, and even less likely to be attending a four-year college.

The underweight babies had a sharply higher risk of suffering at least one chronic illness than did their peers. In addition, they were far more likely to have a neurological disorder, often cerebral palsy, than those in the other group. Indeed, those conditions seem to explain most of their subpar performance in school.

"Once you eliminate the kids with severe cerebral palsy, there's not very much unique about the educational difficulties these kids have," McCormick says.

Yet despite the developmental setbacks, once they reached adulthood these children were no more likely than their peers -- and often somewhat less likely -- to engage in dangerous behaviors. They reported similar rates of alcohol, tobacco and drug use, and they had fewer brushes with police. Young women in the group were also about half as likely to have become pregnant or have given birth than their peers.

"We postulate that the more limited risk-taking behavior that we have documented may result from increased parental monitoring of very low birth-weight children," the researchers write. More follow-up will help flesh out how much schooling the group completes and what careers they pursue, they add.

In an unrelated study, government researchers say babies born a week to a month early are more prone than full-term infants to small developmental delays. The problems, which also beset underweight full-term newborns, involve modest lags in crawling, speaking in sentences and other milestones, and they likely don't last.

However, the researchers say the findings may affect parents' decisions to induce labor or undergo a cesarean. A report on that study appears this month in Paediatric and Perinatal Epidemiology.

Dr. Lynne Haverkos, who oversees some preemie research at the National Institute of Child Health and Human Development, which funded both studies, says the area is of "great interest" to the institute.

"We're highly committed to understanding pre-term deliveries, and are funding a considerable amount of research to identify its causes, consequences and long-term outcomes," Haverkos says.

What To Do

For more on the care preemies receive, check out Neonatology or the Baby Zone.

To learn more about developmental problems, visit the Developmental Disabilities Health Alliance.

SOURCES: Interviews with Marie McCormick, M.D., Sc.D., professor and chairwoman, department of maternal and child health, Harvard School of Public Health, professor of pediatrics, Harvard Medical School, Boston; Lynne Haverkos, M.D., program director, behavioral pediatrics and health promotion research, National Institute of Child Health and Human Development, Bethesda, Md.; Jan. 17, 2002, New England Journal of Medicine
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