Cesarean section or c-section babies have a different microbiome than those born vaginally, according to a new study published on 18 September in Nature, the most comprehensive to date on the newborn microbiome (1).
This may potentially have profound implications on a child’s health as those born by c-section tend to lack key strains of gut bacteria found in healthy children and adults. Moreover, some epidemiological studies suggested c-section babies may have an increased risk of asthma, allergies, and obesity later in life. However, the authors did not look at the impact of these differences on health later in life.
In the womb, babies are in a sterile environment. But as soon as they contact they are exposed to the outside world, they are also exposed to bacteria, which rapidly colonises the gut. Scientists believe this initial exposure could be a defining moment for the immune system and its sensitivity could potentially depend on which microbes the newborn child initially comes into contact with.
The large study led by microbiologist Trevor Lawley at the Wellcome Sanger Institute in Hinxton, UK analysed almost 600 births in the UK. The findings are part of a larger study called the Baby Biome Study, a large-scale study is aimed at determining how microbes and viruses influence the immune system during early childhood.
The researchers collected faecal samples from three hospitals in London and Leicester in the UK and examined the DNA of microbes found in the faeces of 314 babies born vaginally and 282 by c-section at 4, 7 and 21 days after birth.
And they discovered striking differences. As previously suspected, the scientists confirmed that babies born by cesarean section do, indeed, have distinct microbiomes. Compared to vaginally born babies, the microbiota of c-section babies lacked essential bacteria associated with a healthy microbiome and instead, opportunistic bacteria like Enterococcus and Klebsiella, which circulate in hospitals, were found to dominate.
The team are hoping to gather enough data in order to find out whether the type of birth does, in fact, impact a person’s health in adulthood. But there are a number of additional factors to consider. For instance, the antibiotics administered to mothers during childbirth, which can cross the placenta. Moreover, the microbiota of babies born via both modes is similar several months later. By six to nine months, the differences between the two groups could no longer be detected.
Nevertheless, how the immune system functions throughout life might be influenced by those early interactions with bacteria, senior author Dr Nigel Field of University College London told The Guardian. In addition, by pinpointing specific microbes found in vaginally delivered babies, scientists could possibly develop microbe therapies for c-section babies.
However, the authors do emphasise that their findings do not offer support for vaginal seeding – an attempt to restore any missing microbes by swabbing newborn infants with their mother’s vaginal fluids. At present, the safety and effectiveness of the controversial practice remain unproven.
(1) Shao, Y. et al. Stunted microbiota and opportunistic pathogen colonization in caesarean-section birth. Nature (2019). DOI: 10.1038/s41586-019-1560-1