Longer gestation during normal pregnancy is associated with significantly greater development of white matter in babies’ brains. However, similar associations are no longer present by the time children are 8 years old. The lack may confirm that white-matter development in the brains of preemies tends to catch up as these children grow.
That’s according to the authors of a study conducted at the University of Arkansas and published online Oct. 12 in the American Journal of Neuroradiology.
Xiawei Ou, PhD, and colleagues at Arkansas Children’s Nutrition Center used diffusion-tensor MRI (DTI) to evaluate white-matter microstructures in two groups of term-born (≥37 weeks of gestation) healthy subjects: 2-week-old infants (n = 44) and 8-year-old children (n = 63).
The researchers found that markers for the microstructural integrity of white matter—specifically, fractional anisotropy values—positively correlated with gestational age at birth in most major white-matter tracts and regions in the infants.
Further, also in the infants, the team found that diffusivity values (measures of water diffusivities in the brain) and axial and radial diffusivity values (markers for axonal growth and myelination) negatively correlated with gestational age at birth, again in most white-matter tracts and regions.
However, they found no significant correlations with gestational age for any tracts or regions in the term-born 8-year-old children.
Commenting on this latter finding in their discussion, Ou and colleagues write that it may reflect the action of a “catch-up” effect.
Citing prior population-based studies showing that white matter development is associated with cognitive functioning in healthy children, reflected in both imaging and IQ testing, their present results “indicate that white-matter changes are not likely the driving force for reported relationships between gestational age and cognitive performance in term-born children.”
The authors also note prior research showing more changes in gray matter than white matter compared with term controls.
“The development of gray matter, the other major structural component of the brain, may need to be the future focus for exploring potential relationships between gestational age and brain development in term-born children,” they write. “This may be achieved by either global/regional volume or cortical thickness measurements of gray matter or fMRI measurements of stimulated brain activation or connectivity at resting state in gray matter.”
AJNR has posted the Ou et al. study in full for free.