Babies born by caesarean section may have abnormal immune systems and be at greater risk of contracting bloodstream infections from hospital bugs, a new study suggests.
For decades health experts have feared that c-sections prevent babies picking up protective bacteria that they should have been exposed to in the birth canal.
It is known that children born by caesearean are more likely to develop allergies, autism, ADHD, asthma, Type 1 diabetes and be obese, and scientists supected that a misformed microbiome - the collection of bugs in the gut - might be to blame.
Now a seven year study by scientists from University College London (UCL), the University of Birmingham, and the Wellcome Sanger Institute, has found that c-section babies do have a microbiome that is significantly different to babies of natural birth.
Although the experts do not yet know the long-term health consequences, they believe that natural birth is a ‘thermostatic’ moment which primes the immune system. Without exposure to the mother’s gut bacteria, the immune system may not develop normally.
The c-section babies also had more bacteria that are typically acquired in hospitals, which can lead to bloodstream infections.
Dr Nigel Field, clinical associate professor at UCL, said: “We found significant differences between babies born by caesarean and babies born vaginally.
“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 is it presented with.
“And so the hypothesis is that that moment of birth might be a sort of thermostatic 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.”
Britain has one of the highest rates of caesarean section in Western Europe, with 26.2 per cent of the 679,000 births delivered this way, compared with 19.7 per cent in 2000. Nearly half of c-sections are elective, rather than emergency.
New research is the largest ever study of baby microbiomes with scientists analysing 1,679 samples of gut bacteria from 596 babies and 175 mothers. Faecal samples were taken from babies aged four, seven or 21 days old, who had been born in three UK hospitals.
Surprisingly, the scientists found the bacteria in naturally born babies had come from the mother’s gut, rather than the birth canal, suggesting it is exposure to microbes around the perinaeum that is important.
Some clinics in the US offer a practice known as ‘vaginal swabbing’ for c-section babies in which bacteria is collected from the birth canal and placed in the baby’s mouth. But the new study suggests the practice is flawed.
Scientists found the differences in gut bacteria between vaginally born and caesarean delivered babies largely evened out by one-year-old, but large follow-up studies are needed to determine if the early differences influence health outcomes later in life.
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.
“We urgently need to follow up this study, looking at these babies as they grow to see if early differences in the microbiome lead to any health issues.
“Further studies will help us understand the role of gut bacteria in early life and could help us develop therapeutics to create a healthy microbiome.”
Experts from the Royal College of Obstetricians and Gynaecologists say that these findings should not deter women from having a caesarean birth.
Commenting on the study, Andrew Shennan, Professor of Obstetrics at King's College London (KCL), said: “Our microbiome, the bacteria that live on our skin and in our gut, is important to us to ensure optimal health.
“We obtain a lot of this around the time of birth. This important study confirms that the way we give birth will alter our microbiome in the first year of life.
“Caesarean delivery results in fewer bacteria in the baby’s gut being like its mother’s. This is not known to be harmful and mothers who need a caesarean should not be alarmed. The further effects of this in long term health need to be evaluated.”
The research was published in the journal Nature.