New research provides another piece of the puzzle about why babies born by C-section are at increased risk of developing asthma by age 6.

Previous research found marked changes in the baby's gut microbiome associated with being born by C-section.

These marked changes are detectable at 1 week and 1 month, but by age one, in most cases there are only minor differences when compared to vaginal birth.

Within our Microbiome Courses, scientists suggest the marked changes linked to C-section could be due to a baby not being exposed to the "full set" of the mothers' vaginal and gut bacteria associated with the vaginal birth.

As described within our courses, these marked changes could impact the maturation of the infant gut microbes, and in turn impact the optimal training of the infant immune system.

Now new research suggests an important factor that could increase the risk of a baby born by C-section later developing asthma.

The research published in Science Translational Medicine looked at 700 children in the Copenhagen Prospective Studies on Asthma in Childhood2010.

The study found that if by the age 1, there are no changes detectable in the infant gut microbiome associated with being born by C-section, the scientists found no increased asthma risk.

According to this new research paper by Stokholm et al (2020) published in Science Translational Medicine, this indicates a "healthy gut maturation".

"No association with asthma risk was found with gut microbiota perturbations that occurred at birth but resolved by 1 year of age"

However, if the baby's gut microbiome still had the gut microbial signature of a C-section baby by age 1 - an infant could be at increased risk of developing asthma by age 6.

According to the research paper, a microbial signature of a C-section baby by age 1 could triple the risk of asthma.

"However, children delivered by cesarean section who retained a cesarean section gut microbial profile at age 1 year had a three times increased risk of developing asthma by age 6."

This research suggests that a 'healthy' maturation of the gut microbiome during the first year of life may decrease the risk of developing asthma for children born by C-section.

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Scientific reference:

By Jakob Stokholm, Jonathan Thorsen, Martin J. Blaser, Morten A. Rasmussen, Mathis Hjelmsø, Shiraz Shah, Emil D. Christensen, Bo L. Chawes, Klaus Bønnelykke, Susanne Brix, Martin S. Mortensen, Asker Brejnrod, Gisle Vestergaard, Urvish Trivedi, Søren J. Sørensen, Hans Bisgaard, Delivery mode and gut microbial changes correlate with an increased risk of childhood asthma, Science Translational Medicine 11 Nov 2020:Vol. 12, Issue 569, eaax9929 DOI: 10.1126/scitranslmed.aax9929

https://stm.sciencemag.org/content/12/569/eaax9929