Does being born by caesarean section affect intestinal flora?

Chris - When a baby comes out the normal way, I said, quite appealingly, the baby's first taste of life is a mouthful of much which is its mum's muck. Those are bacteria which have colonised mum and have become optimised both to her genetically and also to the food she eats, and environment she inhabits. And therefore it's perfect for the baby because that's the same environment in which the baby is going to grow up.

Babies born by caesarean, as you suspect, when they're inside their mum, they're completely sterile. A baby inside the mother has no bacteria at all in it and on it, and it acquires its bacteria only on the way out of the body. So babies which are whipped out via the caesarean route - where you make an incision in the abdomen and then make a cut through the wall of the uterus, the womb, and you get the baby out that way, those babies are not going to get colonised by flora in the same way as a baby delivered the normal way.

So what do they get? Well people have studied this quite carefully now actually and what they have found is that in fact, the baby picks up bacteria from its immediate surroundings. When it's born by caesarean, that means it picks up bugs from the hospital surroundings and babies born that way tend to get a different spectrum of bacteria, at least initially, compared with babies that are born the normal way. They tend to get more - for instance, Clostridia, for instance, Clostridium difficile which causes C. diff diarrhoea in elderly people for instance. They pick that up. They pick up Staphylococci and they pick up Streptococci, so they get a very different spectrum of bugs which then does eventually change and become more normal and resemble what their family carry. But it's still maybe slightly and subtly different.

There may also be a longer term legacy because doctors have shown that babies born via that route may actually have an increased risk of asthma, allergies and diarrhoea, at least for the initial part of their life and maybe there may be a lifelong risk of those allergy situations.

So the bugs you acquire in the early part of your life have an important role to play in educating your immune system, and they also protect you from diarrheal illnesses because they keep the bad guys at bay.