Breast milk exposure is associated with cortical maturation in preterm infants

Breast milk exposure is associated with improved neurocognitive outcomes following preterm birth but the neural substrates linking nutrition with outcome are uncertain. By combining nutritional data with brain MRI, we tested the hypothesis that high versus low breast milk exposure in preterm infants during neonatal care results in a cortical morphology that more closely resembles that of infants born at term. We studied 135 preterm (mean gestational age 30+2 weeks, range 22+1 to 32+6) and 77 term-born infants (mean gestational age 39+4 weeks, range 36+3 to 42+1). Nutritional data was collected from birth until hospital discharge to identify the proportion of days preterm infants received exclusive breast milk. Structural and diffusion MRI were performed at term-equivalent age. Cortical indices (volume, thickness, surface area, gyrification index, sulcal depth, curvature) and water diffusion parameters (fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity, neurite density index, orientation dispersion index) were compared between preterm infants who received exclusive breast milk for <75% of inpatient days (n=68), preterm infants who received exclusive breast milk for [≥]75% of inpatient days (n=67) and term-born controls (n=77). High breast milk exposure was associated with reduced cortical gray matter volume (d=0.47, p=0.014), thickness (d=0.42, p=0.039) and radial diffusivity (d=0.38, p=0.039), and increased fractional anisotropy (d=0.38, p=0.037) after adjustment for age at MRI. High versus low breast milk exposure in the weeks following preterm birth is associated with a cortical imaging phenotype that more closely resembles the brain morphology of healthy infants born at term.