Children born by caesarean section have fewer helpful bacteria in their gut and this could affect the development of their immune system, a new study has found.

Caesarean babies also have fewer chemicals in their gut, which are known to reduce allergic responses.

Swedish scientists looked at the way in which bacteria colonised in the guts of 24 infants, nine of whom were born via caesarean section. They were assessed one week after their birth and then again one month, three months, six months, 12 months and 24 months later.

Blood samples were also taken at six, 12 and 24 months to test for immune system chemicals known as Th1 and Th2 chemokines. Too much Th2 chemokines are thought to play a role in the development of allergies, however Th1 chemokines can counteract this.

The study found that babies who did not pass down the vaginal canal and were instead born via caesarean had lower levels of Th1 chemokines circulating in their body.

It also found that these babies either lacked the group of gut bacteria known as Bacteroidetes phylum, or they acquired them late. Bacteroidetes phylum have a major role to play in keeping the gut healthy.

The scientists found that in some caesarean babies, they did not acquire these important bacteria until one year after their birth.

Meanwhile, caesarean babies had a lower range of bacteria in their guts overall compared to babies born vaginally.

The scientists from the KTH Royal Institute of Technology emphasised that bacteria are important for getting the immune system ready to respond to triggers in the body and not overreact, which is what occurs in conditions such as allergies and inflammatory bowel disease (IBD).

IBD, which includes Crohn's disease and ulcerative colitis currently affects around 15,000 people in Ireland. Symptoms can include persistent diarrhoea, abdominal cramps and fatigue.

Statistics show that the caesarean rate in Ireland in 2011 was 27%.

Details of these findings are published in the journal, Gut.

For more information on IBD in Ireland, see our Crohn's Disease and Colitis Clinic here