Traditionally, scientists have believed severely premature babies develop and maintain lower-than-average intelligence levels because of brain damage or lack of brain development. But, a study published Wednesday shows, babies who are born 12 to 16 weeks prematurely tend to show improvement in IQ scores as they grow older.

Many of the premature children in the study started out at a below-normal IQ at age 3, but the Yale-led team discovered that by age 8, the IQ scores of the children increased significantly. Yale neurology and pediatrics professor Laura Ment, the lead researcher, followed the children from birth and continues to follow them in her ongoing study.

The study appeared in Wednesday’s Journal of the American Medical Association.

Ment’s primary research interests focus on helping to prevent intraventricular hemorrhage, or IVH, — a serious condition where bleeding in the brain seeps into surrounding fluid spaces — in premature infants. She said she had always intended to do a follow-up on her IVH prevention trials in order to make sure that there were no long term side effects from the drugs. Upon doing these follow-up studies, she said she noticed the children’s improvement in IQ scores and decided to conduct the recent study.

“[This is] good news for parents and physicians who take care of premature babies,” Ment said.

She said children who have lower-than-average IQ levels at a young age are often placed in special education programs, which carry a social stigma of their own.

But Ment found that 71 percent of children who had lower-than-normal IQ’s at age 3 had improved to a nearly normal level by age 8. In addition, 49 percent of those diagnosed as mentally retarded at age 3 were not mentally retarded by age 8.

She said this improvement in IQ was a natural progression, without the help of any active intervention. But she said premature children who received speech therapy early on and children who came from two-parent families were more likely to improve. In addition, those whose mothers either had some higher level of education or joined an intervention program were prone to improvement.

Ment proposed that the strength of her recently published report lies in the fact that it is a “multicenter study,” with babies from all over the United States. She said the study is also longitudinal.

“[The] same kids [were] given the same tests at the same age and at the same time,” Ment said.

Ment’s inspiration for the study? A parent with premature triplets informed her that her children seemed to be getting smarter. The mother turned out to be right.