Premature Infants Have Smaller Brains; Do They Normalize Over Time?

The brains of premature infants are smaller than those of full-term babies, even when measured at the same developmental stage after birth, according to recent studies of brain images at Harvard Medical School and Brigham and Woman’s Hospital.
A number of recent studies have associated educational disadvantages with low birth weight, a hallmark of premature delivery. This deficiency continues into adulthood.
One surprising report that came out in 2000 showed that newborns weighing less than 5.5 pounds are nearly four times more likely to drop out of high school by age 19 than siblings born in the normal weight range. The study did not examine physiological differences.

From the Harvard Medical School :
Premature Infants Have Smaller Brains; Do They Normalize Over Time?

ARLINGTON, Va., March 12, 2003 ? The brains of premature infants are smaller than those of full-term babies, even when measured at the same developmental stage after birth, according to recent studies of brain images at Harvard Medical School and Brigham and Woman’s Hospital.

A number of recent studies have associated educational disadvantages with low birth weight, a hallmark of premature delivery. This deficiency continues into adulthood.

One surprising report that came out in 2000 showed that newborns weighing less than 5.5 pounds are nearly four times more likely to drop out of high school by age 19 than siblings born in the normal weight range. The study did not examine physiological differences.

Simon Warfield, Ph.D., assistant professor of radiology at Harvard University, is studying the physiology using one of the largest databases of magnetic resonance images (MRI) of the brains of both preterm and full-term infants.

“We found that infants with certain brain injuries have a thinner cortex than those of healthy individuals,” Warfield says. “This suggests that preemies are not just delayed compared with healthy infants, but that there are significant structural differences. I don’t know if infants will be able to make up for these.”

Warfield, however, has found that smaller brain size and other structural abnormalities in the brains of preemies may, in fact, persist. “Nobody has really had a look at the brains of infants before,” he says. “Doing MRIs on premature infants is rare.”

With a 2001 Biomedical Engineering Research Grant from the foundation, Warfield combined 285 three-dimensional volumetric MRI images taken since 1994 at Brigham and Women’s Hospital with 20 images from Children’s Hospital in Boston, 70 from Christ Church Hospital in New Zealand, and 106 from Royal Women’s Hospital in Melbourne, Australia. His group standardized the images and placed them in a database that is being used to create a complete model of infant brain development.

“There is no significant data on the normal pattern of structural brain development. We’re building a database on a whole range of ages from 28 to 42 weeks to assess how much brain tissue is present and what is typical,” Warfield says. “The most important characteristic is that this will be quantitative. We won’t be relying on interpretations of behavior to assess development. It will be an objective measure that will tell us about the brain.”

Warfield’s research has already contributed to improvements in care for preterm infants. His work was cited in the American Academy of Pediatrics’ warning to doctors in 2001 about using dexamethasone, a commonly prescribed treatment for lung problems in preterm newborns. The drug eases irritation caused by treating underdeveloped lungs with a mechanical ventilator and a breathing tube. But Warfield and others cited the potential for serious side effects from dexamethasone. They found that the drug treatment was associated with a 30-percent reduction in brain size on MRI scans.

“Now we’re curious what parts of the brain are affected. What areas of the brain are smaller than they should be?” he asks.

Contact:
Simon Warfield, Harvard University
Frank Blanchard, The Whitaker Foundation

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