Premature birth can stunt a child's later development, retarding speech, reading, and social skills–up to 50 percent of babies born early have developmental handicaps during their preschool years and 1 in 5 repeats a grade before he is 8 years old. Boys often seem to be more affected than girls, though no one is sure why. In addition, not much is known about how premature birth affects the brain's white and grey matter–the bunches of neurons that do the bulk of information processing. A collaboration of researchers from Stanford, Yale, and Brown medical schools may have found the answers to both these questions.

What the researchers wanted to know: How are white and gray matter affected by premature birth, and why do boys seem to be more severely affected than girls?

What they did: The researchers compared MRI scans of 65 eight-year olds who were born prematurely to scans from 31 eight-year olds who were born at full term. All of the children in the study lived near New Haven, Conn., were participating in another study on the prevention of brain hemorrhages, and had been examined as infants as part of that study.

What they found: The researchers found that the 8-year olds who were born prematurely had a lower volume of gray matter than children who were born close to their due date. That means that the differences in preemie brain size continues past birth and well into childhood. Prematurely born girls had a similar volume of white matter at age 8 as girls born at full-term, but boys born prematurely had a significantly lower volume, showing their brains had not yet caught up. However, in girls, the amount of gray and white matter in their brain affected their intelligence (with a lower volume associated with less intelligence) while in boys it did not seem to matter.

What it means to you: There are many things besides the volume of neurons in a child's brain that can affect his or her social and intellectual development. However, this study is one of the first to provide solid and specific evidence that premature birth can affect a child's development for years to come. The researchers hope that their study may lead to therapies to enhance the brains of preemies, or perhaps even ways to speed the development of the brain of fetuses that are at high risk for premature birth. (But these things are still light years from being put into practice.)

Caveats: Again, children develop at all different paces for many different reasons–brain size is only one of many factors. In addition, the group that was studied was slightly healthier as babies than most other preemies. But, if that did skew the results, it made the effects appear smaller than they otherwise would have been.

Find out more: The National Institutes of Health has a website with information about premature birth and caring for preemies, updated frequently to incorporate new research: http://www.nlm.nih.gov/medlineplus/prematurebabies.html

Parents of Premature Babies Inc. has a website that is not often updated but has a page with answers to many of the questions that parents of premature babies might have: http://www.preemie-l.org/faqs.html

Read the article: Reiss, A.L. et al. "Sex Differences in Cerebral Volumes of 8-Year-Olds Born Preterm." The Journal of Pediatrics. August 2004, Vol. 145, No. 2, pp. 242-249.

Abstract online: http://www2.us.elsevierhealth.com/scripts/om.dll/serve?action=searchDB&searchDBfor=art&artType=abs&id=as0022347604003300&nav=abs