When born vaginally, infants are exposed to their mothers' microbiomes, but that does not occur during C-sections. As studied have found that babies born by C-section have microbiomes that differ from their vaginally born counterparts and as rates of immune-related diseases also differ between the two groups, some researchers have wondered whether there might be a link. This has led to studies examining whether swabbing newborns born via C-section with their mothers' microbiomes might counteract that effect. However, critics argue there is little data supporting the theory and could expose newborns to disease-causing microbes.
Nature News notes that four such clinical trials are underway, two in the US, one in Sweden, and one in China. "We're trying to repair and partially restore something that is normally in the environment of babies being born," Rutgers University's Maria Gloria Dominguez Bello, who is leading one of the trials, tells Nature News. She adds that controlled trials are the best means of determining microbes' role in infant health.