A downside of the rising number of caesarean (C-section) births is that it deprives babies of contact with bacteria from the mother’s gut microbiome, which impoverishes the baby’s own microbiome and raises the risk of allergies and obesity later in life, as studies show. Previously, researchers swabbed C-section babies’ mouths with vaginal bacteria, but it had no effect. In fact, the valuable gut bacteria are released in the mother’s fecal matter during the messy process of birth.

In a pilot study, doctors from the University of Helsinki tested 17 mothers that were about to need C-sections and chose seven that had fecal matter free of pathogens and antibiotics. After the babies were born, doctors used a syringe to feed the infants a tiny amount of the previously harvested fecal matter mixed with breast milk. The babies had no negative responses. Within three weeks, those babies’ gut flora came to resemble more strongly the gut flora of babies born vaginally than that of those born through C-sections.