AbstractRecent studies suggest that foetal colonisation begins prior to birth. There are other major determinants for neonatal gut colonisation other than that of a possible prenatal transfer of maternal bacteria to the foetus, including the delivery and feeding mode, as well as perinatal antibiotic exposure. Generally, vaginally born infants are first colonised by bacteria from the maternal vagina, whereas the gut microbiota of infants born by caesarean section (CS) more often resembles that of maternal skin and oral microbiota. Indeed, CS delivered babies seem to have a higher incidence of obesity,
type 1 diabetes and asthma. The mode of feeding also plays an important role in influencing early intestinal microbiota. A more eubiotic microbiota composition is conferred to breastfed infants than to their formula-fed counterparts. Nowadays, we have evidence of antibiotic induced intestinal dysbiosis, which is, in turn, associated to an increased risk of developing overweight/obesity, as well as asthma, wheezing and/or inflammatory bowel disease, later in life. Overall, the early gut dysbiosis may have long-term negative effects on an infant’s healthy immunological, hormonal and metabolic development. There has been extensive evaluation of how probiotic supplementation early in life may re-establish gut eubiosis and reduce the negative long-term effects of early dysbiosis. The most commonly used and studied probiotic strains and species include Lactobacilli, Bifidobacteria and S. boulardii. Accumulated evidence in neonatology suggests that some probiotic strains may be effective in preventing antibiotic associated diarrhea, necrotizing enterocolitis in premature infants and/or eczema. L. reuteri may also be effective in treating infantile colic.