The conundrum of intestinal injury in preterm infants receiving mother's own milk.

"Necrotizing enterocolitis" ("NEC") is a heterogeneous group of intestinal injuries experienced primarily in preterm infants. Risk factors include among others preterm gut microbiome alterations. Maternal milk (MM), or otherwise parent milk, is protective for the developing intestine due to its constituents, which include bioactive antimicrobials, immunomodulatory molecules, human milk oligosaccharides (HMOs), secretory immunoglobulin A (sIgA), and microorganisms. However, some preterm infants receiving exclusively mother's own milk (MOM) develop intestinal injuries. Studies showed predisposition to increased risk for "NEC", when a decreased MM HMO, disialyllacto-N-tetraose, is combined with an altered infant's gut microbiome. The intestine may also become more prone to injury with a greater amount of bacteria not bound to IgA. Variations in MM composition may alter the offspring gut microbiome, depriving protection. The different "NEC" entities should be considered to play a role as to why, in many studies, MOM does not provide absolute protection against preterm intestinal injury.