Caesarean babies have different gut bacteria and higher risk of asthma
Babies born vaginally have different gut bacteria than those delivered by caesarean, new research suggests.
Scientists discovered that while vaginally born babies got most of their gut bacteria - microbiome - from their mother, babies born via caesarean did not.
Instead they had more bacteria associated with hospital environments in their guts.
Researchers from the Wellcome Sanger Institute, UCL, the University of Birmingham and their collaborators stress the exact role of the baby's gut bacteria is unclear.
In the study published in 'Nature', they say it is unknown if these differences at birth will have any effect on later health.
Dr Nigel Field, clinical associate professor at UCL, said: "Babies are sterile when they are in the womb.
"And the moment they are born is the moment when the immune system has a huge number of bacteria that it is presented with.
"And so the hypothesis is that that moment of birth might be a sort of thermostat moment which sets the immune system for future life.
"There is research showing that babies born by caesarean section have a slightly higher risk of immune-related conditions. They have a slightly higher risk of asthma, or inflammatory bowel disease and other allergic conditions."
Dr Field added: "In summary, we found significant differences between babies born by caesarean and babies born vaginally, but these babies were healthy when they took part in Baby Biome, and we don't know what the long-term consequences are."
Understanding how the birth process affects the baby's microbiome will enable future research into bacterial therapies.
Researchers studied 1,679 samples of gut bacteria from 596 babies and 175 mothers.
Experts from the Royal College of Obstetricians and Gynaecologists say that these findings should not deter women from having a caesarean birth.
Dr Trevor Lawley, a senior author on the paper from the Wellcome Sanger Institute, said: "This is the largest genomic investigation of newborn babies' microbiomes to date."
Principal Investigator of the Baby Biome Study, Professor Peter Brocklehurst, of the University of Birmingham, said: "The first weeks of life are a critical window of development of the baby's immune system, but we know very little about it."