Earlier studies comparing breast-fed with formula-fed children reported increased abundance ofBifidobacterium species in those who were breast-fed for longer periods of time. All of the children in the current study were breast-fed for some period of time, and while there was some correlation between the length of breast-feeding and levels of Bifidobacteria, some of the children in this group had low levels of those bacteria even while being breast-fed.
Previous studies also have reported finding a particular microbiome signature, with low abundance of the Bacteroides genus in cesarean-section-delivered children during the first six months of life. In the current study, the researchers found the same pattern in the four cesarean-delivered children but were surprised to find it also occurred in seven of the vaginally born children.
No identified factors, including maternal antibiotic treatment, differentiated between vaginally born children with or without the low-Bacteroides signature. Because this pattern has been associated with reduced overall diversity of the microbiome, Xavier noted, it warrants further investigation.