SOURCES: Jennifer Walsh, M.B.B.Ch., consultant neonatologist, Royal Women's Hospital, Melbourne, Australia; Edward McCabe, M.D., Ph.D., senior vice president and chief medical officer, March of Dimes, White Plains, N.Y.; June 10, 2014, Radiology, online
TUESDAY, June 10, 2014 (HealthDay News) -- Being born just a few weeks early may have more impact on brain size and maturity than previously thought, a new study suggests.
Using MRI scans, Australian researchers compared the size and development of various brain structures in babies born between 32 and 36 weeks and those born after 37 weeks of gestation. They found that late preterm birth appears to disrupt the brain growth that would normally occur in the final one to two months of pregnancy.
"What was perhaps not expected was the extent of the differences," said study author Dr. Jennifer Walsh, a consultant neonatologist at Royal Women's Hospital in Melbourne. "Many areas of the brain were affected, and their brains looked less mature than might have been anticipated."
The study is published online June 10 in the journal Radiology.
Each year in the United States, one in every eight babies is born prematurely, which is defined as before the 37th week of pregnancy, according to the U.S. Centers for Disease Control and Prevention. Full-term pregnancy is considered 40 weeks.
Late preterm babies account for about 80 percent of all premature births, though the vast majority of research focuses on preemies born before 32 weeks, study authors noted. Many premature babies thrive, but long-term health conditions can result, including intellectual difficulties, cerebral palsy or problems with breathing, vision and hearing.
Walsh and her colleagues performed MRI exams on 199 late preterm infants and 50 infants born after 37 weeks of pregnancy in the weeks after birth. While brain injury rates between the two groups were similar, late preterm infants had less-developed myelination -- a fatty insulating sheath around nerve fibers -- in one part of the brain.
These infants also exhibited more immature gyral folding, which is the folding of the gray matter that increases the brain's surface area. Myelination and gyral folding are both thought to be important processes in early brain development.
Scientists aren't yet sure what these brain differences mean, Walsh said, and more research is required.
"It's not yet known if these findings will be associated with any adverse long-term outcomes for the babies in the study," she said. "That's the next stage of [our] project. Parents of [these] infants should not be concerned at this stage . . . The most important thing [is to] listen to the advice of their pediatrician."
Dr. Edward McCabe, senior vice president and chief medical officer of the March of Dimes, said that the new research underscores the notion that not just babies born very prematurely suffer health consequences.
Obstetricians and expectant parents who feel it's acceptable to schedule a cesarean section or induce delivery at 37 weeks of pregnancy need to know that those extra three weeks to reach full term are necessary for the baby's optimal development, he said.
"I'm a pediatrician and a geneticist," McCabe said, "and I've always said that we haven't invented a better incubator than the womb."
The U.S. National Library of Medicine offers more information about preterm infants.