They are mum’s first gift to her newborn baby on the day of its zeroeth birthday – bacteria, fresh from her vagina. Vaginal bacteria are among the trillions of microscopic hitchhikers that share our bodies with us. Collectively known as the ‘microbiota’, these passengers outnumber our own cells by ten to one. Children partly inherit their microbiota from their mothers. During birth, they pass from the largely bacteria-free conditions of the womb through the microbe-laden vagina into the equally bacterial outside world.

Being slathered in vaginal microbes might not seem like much of a treat from our adult perspective, but to a newborn, it’s a key event. The microbiota are important partners, influencing our physiology and our risk of disease. Now,