Dhe human body is dependent on bacterial organisms that help with digestion and help shape the immune system. Their entirety is called the microbiome, and scientists have been paying a lot of attention to it in recent years. A team led by Wouter de Steenhuijsen Piters from the University Hospital Utrecht is now reporting in the specialist journal “Cell Host & Microbe” on research results on the question of how bacteria are transmitted from mothers to their children.
Specifically, the researchers compared natural, vaginal births with caesarean sections, in which the children do not come into contact with bacteria in the birth canal – this had been suspected as a possible reason for the slightly increased risk of asthma or obesity in caesarean births. Using genetic analysis, the team examined the bacterial composition in samples from 120 mother-child pairs that had been taken from different bacterial “niches”: for example in the nasopharynx, on the skin and in the stool, and also in the mother’s milk and vagina. They sometimes took several samples from the babies over the first month after birth.
Microbiome is most similar right after birth
According to the research team’s analyses, almost 60 percent of the composition of the children’s microbiome can be explained by that of the mothers; it is known that fathers, siblings or the rest of the environment can also play a role. In the approximately 40 percent of children born by caesarean section, whose samples were examined as part of the study, they found lower transmission of microbes from mothers to their children in the stool – on the other hand, bacteria from breast milk were found more frequently in these children than in those who gave birth vaginally.
Immediately after birth, the microbiome of mothers and children was most similar, after that, the babies continue to develop in their own way. The existence of siblings also played a role in bacterial composition, but the type of birth and feeding of the newborns had a much greater influence.
“This is a very well-founded study,” explains the pediatrician Christoph Haertel from the University Hospital of Würzburg, who was not involved in the study, to the Science Media Center. In order for children born by caesarean section to come into contact with their mother’s bacteria, they are sometimes brought into contact with vaginal secretions after birth. To his knowledge, it has not yet been proven whether this has a positive effect in relation to the risk of illness, says Härtel, but at the same time it also harbors risks.
“Now there are first scientific indications that breastfeeding and cuddling can have a similar effect on the microbiome – in addition to many other positive effects,” says the pediatrician. The new data showed that caesarean children benefit greatly from breastfeeding. And the contact with the mother’s skin when cuddling, which also transmits bacteria to the child, ensures greater diversity in this maturing ecosystem, which in turn has a protective effect.
Different paths apparently lead to a healthy microbiome
However, there are still many unanswered questions – such as how the bacteria in the intestine communicate with each other and with the brain. “The bottom line is that you can’t say that all problems can only be solved by breastfeeding,” says Härtel – even if it can have a beneficial effect on intestinal colonization and caesarean section children could get a healthy microbiome in other ways than babies delivered vaginally.
Bernhard Resch from the Medical University of Graz assesses the results in a similar way. It would certainly not have been intended by nature to plan only one path for colonization with bacteria, he says. “It seems to me much more attractive to lay the child on your breast after a caesarean section than to wipe its face with a cloth soaked in vaginal secretion,” explains Resch.