Brains of babies born very prematurely do not develop as well as those who are carried to full-term

Nov 20 2005

The brains of babies born very prematurely do not develop as well as those who are carried to full-term, according to new research presented at the annual meeting of the Society for Neuroscience in Washington, D.C.

Dr. Sandra Witelson, a professor of psychiatry and behavioural neurosciences at the Michael G. DeGroote School of Medicine at McMaster University and chief investigator on the interdisciplinary project at Hamilton Health Sciences, said that an ultrasound study of the brains of babies born around 26 weeks gestation showed that certain aspects of brain development were very compromised compared to infants in utero.

"These findings indicate that the normal early maturation of the brain may be compromised when it takes place outside of the womb," said Witelson, holder of the Albert Einstein/Irving Zucker Chair in Neuroscience at McMaster. "We found that in very premature babies, a part of the brain doesn't show normal growth after birth, and in fact some parts of the brain didn't change at all from the day the babies were born until they reached what would have been a full-term birth date."

These results have clinical relevance in how premature babies are cared for, as they indicate that the early brain may be compromised by being subjected to complex stimulation too early.

The results are based on a study of 80 premature boys and girls whose birth weight was less than 1,000 grams (about 2.2 pounds), and who were born just 26 weeks into a normal 40-week pregnancy. Clinical ultrasounds of the premature infants' brains were done at birth and again when they were discharged from hospital, generally around 36 weeks since conception.

They were compared to the brain ultrasounds taken in utero at about 26 weeks gestation and at birth in other studies to a matched group of 38 full-term infants.

Measurements taken from the ultrasounds showed that certain frontal portions of the brains of the premature babies were comparable at birth to the brains of babies still in utero at that stage of gestation. However, after about 10 weeks in intensive care, the second measurement of the premature babies' brains showed some portions of the front part of the brain were significantly smaller than those of babies who were born at or near full-term.

Dr. Witelson said the findings indicate further research is needed to try to understand what mechanisms in utero are missing after birth that are essential for the normal process of neuro development.

When a fetus's brain is developing during pregnancy in utero, very little patterned sensory stimulation reaches the brain, she explained. The eyelids are closed, the infant is bathed in fluid and minimal sounds are perceived.

In contrast, once the premature infant is born, he is necessarily bombarded by a complex environment full of sights, sounds, touches and unnatural loss of movement.

"This research suggests that stimulation of the brain while it is still under construction may not be beneficial," said Dr. Witelson. "The prefrontal regions appear particularly vulnerable. Is it because they are the most premature at birth?"

The prefrontal regions of the brain that were most affected by the lack of development are important for numerous intellectual functions, including attention, planning and social judgment.

Dr. Witelson said more research is needed to consider what in utero mechanisms are essential for brain maturation and the optimal conditions and treatment needed to foster brain development for very premature infants who are treated in neonatal intensive care units early in life.

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