Babies born vaginally have different gut bacteria - their microbiome - than those delivered by Cesarean, research has shown. Scientists from the Wellcome Sanger Institute, UCL, the University of Birmingham and their collaborators discovered that whereas vaginally born babies got most of their gut bacteria from their mother, babies born via cesarean did not, and instead had more bacteria associated with hospital environments in their guts.
The exact role of the baby’s gut bacteria is unclear and it isn’t known if these differences at birth will have any effect on later health. The researchers found the differences in gut bacteria between vaginally born and cesarean delivered babies largely evened out by 1 year old, but large follow-up studies are needed to determine if the early differences influence health outcomes. Experts from the Royal College of Obstetricians and Gynecologists say that these findings should not deter women from having a cesarean birth.
Published in Nature today (18th Sept), this largest ever study of neonatal microbiomes also revealed that the microbiome of vaginally delivered newborns did not come from the mother’s vaginal bacteria, but from the mother’s gut. This calls into question the controversial practice of swabbing babies born via cesarean with mother’s vaginal bacteria. Understanding how the birth process impacts on the baby’s microbiome will enable future research into bacterial therapies.
The gut microbiome is a complex ecosystem of millions of microbes, and is thought to be important for the development of the immune system. Lack of exposure to the right microbes in early childhood has been implicated in autoimmune diseases such as asthma, allergies and diabetes. However, it is not fully understood how important the initial gut microbiome is to the baby’s immune system development and health, how a baby’s microbiome develops, or what happens to it with different modes of birth.
To understand more about the development of the microbiome, and if the delivery method affected this, researchers studied 1,679 samples of gut bacteria from nearly 600 healthy babies and 175 mothers. Faecal samples were taken from babies aged four, seven or 21 days old, who had been born in UK hospitals by vaginal delivery or caesarean. Some babies were also followed up later, up to one year of age.
Using DNA sequencing and genomics analysis, the researchers could see which bacteria were present and found there was a significant difference between the two delivery methods. They discovered that vaginally delivered babies had many more health-associated (commensal) bacteria from their mothers, than babies who were born by cesarean.
Dr Trevor Lawley, a senior author on the paper from the Wellcome Sanger Institute, said:
"This is the largest genomic investigation of newborn babies’ microbiomes to date. We discovered that the mode of delivery had a great impact on the gut bacteria of newborn babies, with transmission of bacteria from mother to baby occurring during vaginal birth. Further understanding of which species of bacteria help create a healthy baby microbiome could enable us to create bacterial therapies.”
Previous limited studies had suggested that vaginal bacteria were swallowed by the baby on its way down the birth canal. However, this large-scale study found babies had very few of their mother’s vaginal bacteria in their guts, with no difference between babies born vaginally or by cesarean.
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