Verbal and IQ Scores Improve As Premature Infants Grow, Yale Researchers Report

The majority of low birth weight infants show improvements over time in verbal and IQ scores, Yale researchers report in the February 12 issue of the Journal of the American Medical Association.

“These are among the first results to show that the brain may recover from injury over time,” said principal investigator Laura Ment, M.D., professor of pediatrics and neurology at Yale School of Medicine, who began the study after one of the parents in a separate follow-up study remarked that her triplets were getting smarter. “My colleagues and I decided to investigate and are happy to report these positive findings.”

By eight years of age, the children in the study increased their Peabody Picture Vocabulary IQ score by 11 points from 88 to 99. A score of 100 is the average for normal birth weight eight-year-olds.

Starting in 1989, Ment and her colleagues looked at 296 children who weighed between 600 and 1,250 grams at birth. The children had been part of the separate follow-up study since they were six hours old. That study tested the effects of the anti-inflammatory drug indomethacin for preventing intraventricular brain bleeding in premature infants.

Ment and her colleagues tested the children’s verbal comprehension using the Peabody Picture Vocabulary Test-Revised and tested their intelligence using the Wechsler intelligence scales at intervals of 36, 54, 72 and 96 months corrected age.

“We found that children in two-parent households and those with mothers who had higher levels of education increased their IQ scores best,” said Ment. “Children whose mothers had lower educational levels, but received special services, such as physical therapy, occupational and speech therapy also increased their IQ scores.”

Ment said the only children who did not do well were those with brain bleeding at six hours combined with additional brain injury. Animal studies have suggested that there is recovery after injury in a developing brain, meaning the brain is actually making more neurons.

Senior author Robert Makuch said there is hope for these children as well. “With ongoing services these children can benefit greatly from interventions,” he said.

Ment said the next step is to replicate the study and to use MRI to analyze the brain volume of these children. One of her previous studies had shown that the children’s brains at age eight are smaller than brains of normal birth weight eight-year-olds. She will look at the brain volume at age 12 to determine if the brain differences remain the same or decrease over time.

Other authors on the study were Betty Vohr, M.D., of Brown University School of Medicine; and Yale researchers Walter Allan, M.D., Karol Katz, Karen Schneider, Michael Westerveld and Charles Duncan, M.D.

The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS).

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Karen N. Peart: karen.peart@yale.edu, 203-432-1326