The microbiome form infants born prematurely has a different development than that of term born infants. The number of bacteria is reduced, colonization occurs at a slower pace and the diversity is reduced. Many factors may play a role, including a reduced motility of the intestinal tract and a less well developed immune system, both specific and non-specific. Mucus layer, produced by the goblet cells, is reduced and also the composition is altered. Together these factors may play a dominant role in the development of necrotizing enterocolitis (NEC), a condition that develops in approximately 3–10% of all very low birth weight infants. Interestingly, NEC is not observed in utero, very rarely in term infants and also not in preterm infants receiving total parenteral nutrition. Type of enteral nutrition clearly plays a role as the incidence is greatly reduced in infants who are receiving human milk as opposed to formula. A recent study showed that some exposure to cow's milk based formula in early life does not increase the risk of NEC, indicating that protective factors in human milk are responsible for a lower incidence of NEC in preterm infants. Probiotics are mentioned as an effective, cheap and save intervention reducing the NEC rate, but the meta-analyses prevent firm conclusions on what strain(s), dose and time to start. The largest study, published last year, n = 1315, using Bifidobacterium breve as strain did not support the use of probiotic supplementation to reduce NEC rates, whereas the meta-analyses show an overall high effect rate of probiotics. However, we should refrain from pooling data on different probiotics to avoid misleading consumers, parents, and health care professionals. We need data on individual probiotic strains, not on probiotics in general.
AMC & VU University Medical Center Amsterdam The Netherlands