By Callan Emery, Editor
A study published in Nature in September has caught the attention of the media and the interest of
Obs-Gyn specialists. In what is the largest study of the neonatal microbiome (gut bacteria), the researchers provide strong evidence that the way a baby is born impacts significantly on their microbiome.
The study by Lawley T., et al. (doi: 10.1038/s41586-019-1560-1) found that babies born through the vaginal canal carry different microbes from those delivered through caesarean section. Those born through c-section tended to lack strains of gut bacteria found in healthy children and adults. Additionally babies born through c-section showed a high-level of colonization by opportunistic pathogens associated with the hospital environment (including Enterococcus, Enterobacter and Klebsiella species).
Interestingly, the researchers note that it was the mother’s gut bacteria, and not vaginal bacteria, that made up much of the microbiome in the vaginally delivered babies. Previous studies had suggested that vaginal bacteria were swallowed by the baby on its way down the birth canal. This led to what is has been termed ‘vaginal seeding’ whereby babies born by c-section are swabbed with the mothers vaginal fluids in an effort to restore any missing microbes. However, a study by Stinson et al. (doi: 10.3389/fmed.2018.00135) has shown vaginal seeding to be unjustified and potentially unsafe.
Although a lack of exposure to the right microbes in early childhood has been implicated in autoimmune diseases, such as asthma, allergies and diabetes, 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, who analysed nearly 600 births in the United Kingdom, say the differences in gut bacteria between vaginally born and caesarean delivered babies largely evened out by 1 year old. They note that large follow-up studies are needed to determine if the early differences influence health outcomes.
Discussing her study, Stinson pointed out that microbes thrown out of balance in babies born by c-section are very similar to those thrown off balance in babies born to mothers receiving antibiotics but delivering vaginally. She surmises that routine antibiotic administration given to mothers delivering by c-section could be a cause of the bacterial difference in the neonatal microbiome.
Although this research does pose interesting questions about the potential health outcomes associated with c-section versus vaginal delivery, it should be emphasised that at this point mothers should not be deterred from c-section delivery if it is the right choice for the mother and her baby.
The study is part of larger effort, called the Baby Biome Study, which aims to follow thousands more newborns into childhood.