Researchers have discovered that infants who are delivered by caesarean section have a lower range of good gut bacteria in their first 2 years of life, compared with infants delivered through the mother’s birth canal.

The study, published in the BMJ journal Gut, reveals that lower levels of beneficial gut bacteria has implications for the development of the immune system, particularly as infants delivered by C-section also showed lower levels of chemicals responsible for the prevention of allergies.

Researchers from Sweden analyzed the guts of 24 infants. Nine of these infants were delivered by C-section, while 15 were delivered vaginally.

The study authors used high-throughput DNA sequencing to determine microbial composition in fecal samples. These samples were collected from the infants at 1 week after birth, then at 1, 3, 6, 12 and 24 months after birth.

Blood samples were also taken at 6, 12 and 24 months. This was to test for levels of immune system chemicals Th1 and Th2 associated chemokines. Excess Th2 chemokines play a part in the development of allergies, and Th1 chemokines combat this development.

The results of the study revealed that babies delivered by C-section were missing one of the major groups of gut bacteria, the Bacteroidetes phylum, compared with the babies who were born vaginally.

Additionally, some C-section infants did not acquire the Bacteroidetes until 12 months of age.

The researchers add that the total range of bacteria among infants delivered by C-section were lower compared to the infants who were delivered through the mother’s birth canal.

The infants delivered by C-section also showed lower circulating levels of Th1 in their blood, showing an imbalance between Th1 and Th2 chemicals. This means the babies could be more susceptible to developing allergies.

The Bacteroidetes are important for priming the immune system to respond appropriately to triggers, the researchers say. When the immune system overacts through a lack of good gut bacteria, this can lead to allergies, diabetes and inflammatory bowel disease.

Two of the study authors – Anders Andersson, researcher at KTH Royal Institute of Technology and Science for Life Laboratory in Stockholm, and Maria Jenmalm, researcher at Linköping University – explained what this research shows, telling Medical News Today:

Infants born by vaginal delivery typically shared more bacterial species with their own mother than with other mothers, while this could not be shown for infants born by caesarian section.”

They added:

Our study shows that members of the mother’s gut microbiota are transferred to the child during vaginal delivery and that caesarian section leads to an altered colonization pattern of the infant’s lower intestine.”

The researchers say that previous studies have shown an association between C-section and allergy, as well as an association between allergy and a lower microbial diversity of the gut. They add:

Our current study provides a link between these associations by showing that caesarian section leads to a lower bacterial diversity of the gut, and may hence explain the association between caesarian section and allergy.”

The researchers say that this study could lead to further investigations as to whether transfer of maternal vaginal and fetal bacteria to infants delivered by C-section could normalize their microbiota development.

They add that it would also be interesting to investigate whether supplementation of probiotic bacteria to infants delivered by C-section could stimulate their immune maturation and prevent the development of allergies.