PHILADELPHIA -- Children who are born weighing less than about 3 pounds have more medical and behavior problems at school age than children who start out life at a normal size, a new study has found.
The study, centered at Children's Hospital of Philadelphia, offers one of the most complete pictures to date of what happens later in life to babies who are born so tiny that they spend their early days just struggling to survive.
"Children under 3 pounds are two to three times more likely to have problems" when they reach school age compared with children who weigh more than 5 1/2 pounds at birth, said Dr. Marie McCormick, a former Children's Hospital researcher now at the Harvard School of Public Health.
The study, published in today's Journal of the American Medical Association, found that low-birth-weight babies not only are at increased risk for previously well-documented neurological problems -- such as mental retardation, cerebral palsy and seizure disorders -- but also are more apt to have asthma, behavior problems and learning difficulties.
"These children . . . have a higher risk for the common problems that affect children," McCormick said in an interview.
One encouraging find is that "over half of these children appeared relatively healthy, without developmental problems at school age," she said.
The study looked at 1,868 children ages 8 to 10 who had been part of two previous studies on low birth weight. The children had been cared for in infancy at any of 13 hospitals, including Children's Hospital.
McCormick and her colleagues looked at the youngsters' mental health and overall physical health, using 17 different medical conditions.
The lower the birth weight, the greater the likelihood the child would grow up having one or more problems, the researchers reported.
In babies classified as "extremely low birth weight" -- under about 2.2 pounds -- nearly half of the children had IQ scores under 85. (An IQ of 70 is generally considered the threshold of mental retardation. The norm for Americans is 100.)
Among these babies under 2.2 pounds, the low IQ scores held true whether the mother finished high school or not, the study found. But among slightly bigger babies, the mother's level of educational achievement seemed to play a difference, a finding that researchers said underscored the important role the environment can play in a child's development.
McCormick said the results of the study point to the need for follow-up care and early intervention programs for low-birth-weight babies, because their problems clearly do not end when they are discharged from the intensive-care nursery.
Also, she said, more efforts need to go toward preventing the birth of tiny babies in the first place. In the United States, about 1 in every 100 babies is born weighing less than about 3.3 pounds, McCormick said.