Changes in neonatal regional brain volume associated with preterm birth and perinatal factors.

Background: Preterm birth is associated with altered brain development, with younger gestational age (GA) at birth often associated with greater brain volume reduction. Such volume alterations at term equivalent age (TEA) have been found with differing magnitude across different brain regions, although this has mostly been investigated with regards to whole tissue volumes and large-scale subdivisions. In addition to degree of prematurity, many other perinatal factors have been found to influence brain structure and development in infants born preterm. We aimed to clarify the relationships between degree of prematurity and regional brain volumes at TEA, and between perinatal factors and regional brain volumes at TEA, in finer spatial detail.

Methods: 285 preterm and term-born infants (GA at birth 24.6-42.1 weeks; 145 female; 59 born at term) were scanned at TEA. Data on perinatal factors were obtained by chart review, including sex, multiple birth, birthweight standard deviation (SD) score, postnatal growth and social risk. The Melbourne Children's Regional Infant Brain (M-CRIB) atlas was registered to the current sample, then 100 brain regions were labelled for volumetric analyses. Linear regressions with generalised estimating equations and likelihood ratio tests were performed to investigate whether GA at birth or perinatal factors were associated with regional volumes at TEA.

Results: Younger GA at birth was associated with smaller volumes at TEA in some regions including bilateral cerebral white matter, middle temporal gyri, amygdalae, pallidum and brainstem. In other regions, younger GA at birth was associated with larger volumes, including in primary visual, motor and somatosensory cortices. Positive associations between perinatal factors and regional volumes at TEA were found in many brain regions for birthweight SD score, and male sex, independent of GA at birth. These associations were seen on both univariable analyses, and multivariable analyses controlling for other perinatal factors. Social risk and multiple birth were generally not associated with regional brain volumes, and postnatal growth was associated with volume in many regions only after adjusting for other perinatal factors.

Conclusions: These results elucidate regional brain volume differences associated with preterm birth and perinatal factors at a more detailed parcellated level than previously reported, and contribute to understanding of the complex array of correlates of preterm birth.