10% Human : How Your Body's Microbes Hold the Key to Health and Happiness

Once again, we can take instruction from the koala, and other marsupials, this time about the importance of the oligosaccharide content of milk. Most marsupials have two teats, which are inside the pouch. Only one of these is used by the joey for the duration of its suckling life. If two joeys are born in two consecutive seasons, they each have their own teat. Remarkably, the two teats provide milk that is tailored to the age of each joey. The newborn receives milk high in oligosaccharides and low in lactose, whereas the older joey receives a lower dose of oligosaccharides, but far more lactose. Once a joey has left the pouch, the oligosaccharide content of its milk supply drops even further.

Rob Knight and Maria Gloria Dominguez-Bello, an associate professor in the Department of Medicine at New York University, are now running a large clinical trial to establish whether transferring microbes from a woman’s vagina to her newborn might ameliorate some of the short- and long-term effects of C-sections. The experimental technique is simple: a small piece of gauze is inserted into the mother’s vagina an hour before she is due to go into the operating theatre. Just before the first cut is made, the gauze is removed and placed in a sterile pot. A few minutes later, when the baby is out, it is rubbed with the gauze – first in its mouth, then across its face, and then over the remainder of its body.

As it emerges from its mother, it gets another dose of microbes alongside those from the vagina. Disgusting as it may sound, ingesting faeces early in life is not unique to koalas. During human labour and birth, the contraction-inducing hormones and the pressure of the descending baby cause most women to defecate. Babies tend to be born head first and facing towards their mum’s bottom, pausing for a moment with their heads and mouths in prime position whilst their labouring mothers wait for the next contraction to help them ease the rest of the body out. Whatever your instinctive revulsion, it’s an auspicious start. After birth, the mother’s gift of a new coat of microbes, both faecal and vaginal, makes for a simple and safe birthday suit for the newborn.
It’s also probably an ‘adaptive’ start. That is, it’s probably no bad thing that the anus is so close to the vagina, or that the hormones that bring on contractions in the uterus have the same effect on the back passage. Natural selection may have made it that way because it benefits baby, or at the very least causes no more harm than good. Receiving a gift of the microbes, and their genes, that have worked in harmony with your mother’s genome gets you off to a great start.