High Breast Milk Exposure Improves Cortical Maturation in Preterm Infants

A potential dose-dependent relationship may exist between breast milk exposure and brain morphology changes among preterm infants. Preterm infants with high breast milk exposure had cortical imaging phenotypes closer to term-born infants compared with those without high breast milk exposure. These are the findings of a study published in the Annals of Neurology.

Among infants born preterm, breast milk feeding has been associated with improved neurocognitive outcomes and academic performance as well as enhanced brain growth and white matter microstructures. Despite these observations, the relationship between breast milk exposure and cortical development among preterm infants remains unclear.

Researchers from the University of Edinburgh in the United Kingdom recruited 135 preterm infants born before 32 weeks’ gestation and 77 term-born control infants between 2017 and 2020. Magnetic resonance imaging (MRI) findings were compared between preterm and term-born infants at term-equivalent ages. High breast milk exposure was defined as 75% or more of inpatient days with exclusive breast milk feeds and low breast milk exposure as less than 75% exclusive breast milk inpatient feed days.

Among preterm infants, 68 had low breast milk exposure and 67 had high breast milk exposure. The low breast milk, high breast milk, and control groups comprised infants born at an average of 29-, 30-, and 39-weeks’ gestation (P <.001); 51%, 69%, and 52% were boys; their average birthweights were 1289, 1410, and 3484 g (P <.001); 28%, 40%, and 49% were delivered vaginally (P =.041); and 32.4%, 19.4%, and 22.1% received a mixture of breast milk and formula (P <.001), respectively.

The infants in the term-born cohort had higher gyrification index (d, -0.59; P =.001), surface area (d, 0.61; P <.001), and cortical orientation dispersion index (d, -0.45; P =.005) and lower mean cortical mean diffusivity (d, 0.64; P <.001) and axial diffusivity (d, 0.84; P <.001) compared with preterm infants with high breast milk exposure.

Compared with low breast milk exposure, infants in the high exposure group had a lower relative cortical gray matter volume (d, 0.47; P =.014), cortical thickness (d, 0.42; P =.039), and mean cortical radial diffusivity (d, 0.38; P =.039) and higher mean cortical fractional anisotropy (d, -0.38; P =.037).

In the fully adjusted model and after propensity score weighting, infants in the low and high breast milk cohorts differed significantly for cortical gray matter volume (d, 0.46; P =.028) and mean cortical fractional anisotropy (d, -0.39; P =.038).

Stratified by breast milk quartile, significant differences were observed for mean cortical fractional anisotropy (β, 0.223; P =.007), mean cortical radial diffusivity (β, -0.225; P =.0077), and cortical gray matter volume (β, -0.192; P =.017).

This study may have been limited by not having the power to evaluate the difference between donor and maternal breast milk.

These data indicated that among preterm infants, higher exposure to breast milk in the weeks after birth associated with imaging features more closely resembling that of term-born infants compared with preterm infants with lower breast milk exposure.

“Breast milk may offer an intervention to optimise early cortical development following preterm birth, thereby reducing the risk of later neurocognitive impairment and psychiatric disease,” the researchers concluded.