White matter microstructure is influenced by extremely preterm birth and neonatal respiratory factors

The aim of this study was to investigate whether prematurity per se or perinatal risk factors explain altered brain structure after preterm birth, in extremely preterm (EPT) infants without focal brain lesions.

A population-based cohort of 58 EPT infants [gestational age (GA) <27 + 0 weeks] was examined with diffusion magnetic resonance imaging at term-equivalent age and compared with 14 term-born controls. Associations of diffusion measures with prematurity and neonatal risk factors were explored. Data were analysed with tract-based spatial statistics (TBSS) for whole-brain analysis and region-of-interest (ROI) analysis.

Whole-brain analyses showed lower fractional anisotropy (FA) and higher mean diffusivity (MD) in several white matter (WM) tracts in the preterms, which was essentially confirmed by ROI analyses. Within the preterm GA range (23 + 0 to 26 + 6 weeks), GA at birth was not significantly associated with diffusion measures. Bronchopulmonary dysplasia predicted lower FA in the corpus callosum and right inferior longitudinal fasciculus; mechanical ventilation >2 days was predictive of higher MD in the right external capsule.

White matter microstructure is influenced by preterm birth and by neonatal respiratory factors, whereas the degree of prematurity within the EPT range appears to be of less importance.