U.S. study finds brain undeveloped in premature infants

CHICAGO, Illinois (Reuters) -- A study of children born prematurely found that key areas of their brain were still dramatically smaller eight years later, an indication the brain does not always develop properly once a child leaves the womb, doctors reported Tuesday.

The smaller sizes were linked to cognitive impairment as measured by IQ tests, the study from the Yale and Brown schools of medicine said. Researchers who used magnetic resonance imaging to make the determination said it was believed to be the first time brain volume has been measured in premature children.

"The differences in brain volume on average were dramatic in all regions, with reductions ranging from 11 percent to 35 percent," said Bradley Peterson, a Yale professor who headed the study.

"Not all children born prematurely showed these abnormalities, but those born at a younger gestational age were most affected. The magnitudes of the abnormalities in fact were directly proportional to how early the children were born, and they were strongly associated with IQ of the children at age 8 years," Peterson said.

The research involved 25 children born at from 26 weeks to 33 weeks gestation, part of a group of 370 who have been followed since birth. They were contrasted to 39 comparable children who were from 37 weeks to 42 weeks at birth. Full term is 40 weeks gestation.

The premature group weighed on average a little over 2 pounds at birth compared to more than 7 pounds for the full-term children.

Peterson said some areas of the brain where the size disparity was greatest were the sensorimotor regions and temporal cortices that are associated with verbal and performance IQ scores.

"The greater the volume of abnormalities, especially in the cortical regions, the lower the IQ measures," he said.

The study showed that when brains develop prematurely outside of the womb, they are vulnerable to developmental disturbances, Peterson added.

"We now need to find out what precisely is responsible for the problems with brain development in these infants -- from a missing unidentified growth factor, to the absence of physiological buffering by the mother's uterus, to the many medical problems associated with prematurity," he said.

Copyright 2000 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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