Metabolism-related microRNAs in maternal breast milk are influenced by premature delivery

Maternal breast milk (MBM) provides optimal nutrition for growth and development of infants. However, premature infants face a variety of physiological challenges that differ from infants born at term, and therefore they have different nutritional needs from maternal milk. When compared with the milk of mothers with term infants (tMBM), the milk of mothers with preterm infants (pMBM) has higher concentrations of protein, nitrogen, fat, phospholipids, and elements such as sodium, chloride, and iron (1, 2). Conversely, there are lower levels of lactose and zinc in pMBM compared with those in tMBM (1, 2, 3). Macronutrient profiles in MBM also vary with gestation of delivery. An example of this includes lipids: medium-chain fatty acids are higher in pMBM, but levels of oleic acid are lower (1). Analysis of the nutritional sufficiency of pMBM shows that nutrients received per volume of MBM exceed the intrauterine requirements for a given gestational age. In addition, preterm infants fed pMBM receive more nutrients than if they were fed tMBM (1, 2). The importance of these differences in pMBM and tMBM is highlighted by findings that preterm infants fed pMBM have improved health outcomes compared with the preterm infants fed tMBM (4).