Even moderately preterm infants exhibit brain abnormalities

MRI studies have revealed that moderate and late preterm (MLPT) babies—born 32 to 36 weeks into gestation—have similar brain abnormalities as those of very preterm infants born prior to 32 weeks of gestation.

Among these abnormalities are a smaller brain size, less-developed myelination and immature gyral folding, according to the study published online June 10 in Radiology.

“These brain changes may form the basis of some of the long-term neurodevelopmental deficits observed in MLPT children,” wrote lead author Jennifer M. Walsh , MB, BCh, BAO, MRCPI (Pediatrics), of Royal Women’s Hospital in Parkville, Australia, and colleagues.

Walsh and colleagues noted that most of the existing research on the brain development of preterm babies has focused on those born very preterm, but the interest in MLPT birth has grown along with MLPT rates. This group represents about 80 percent of all preterm births and the rising rates of preterm birth over the last 20 years is mostly attributed to MLPT babies.

For the current study, T1- and T2-MR images from 199 MLPT and 50 term-born infants were compared for differences in size and development.

Results revealed that while there were low rates of injury overall in both groups, MLPT infants had smaller brains and larger cerebrospinal fluid spaces. Brain biparietal diameter, deep grey nuclei, cerebellum and corpus callosum measurements were all smaller for MLPT infants compare with those born full-term.

Maturation was affected, as MLPT infants had less mature gyral folding, which increases brain surface area, and less complete myelination of the posterior limb of the internal capsule at term-equivalent age, according to Walsh and colleagues.

“These findings suggest that the expected trajectory of brain growth that would normally occur in the last approximately 2 months in utero (31–34) may be disrupted by MLPT birth, and this disruption may help to explain the basis of the poorer long-term neurodevelopmental outcomes of MLPT infants,” wrote the authors.

MLPT children can face deficits such as motor and cognitive delay. Walsh and colleagues added that further information about brain structure and function is being assessed in this study cohort using measures of diffusion and functional connectivity.