But that doesn’t mean you can smear poo on your newborn baby’s face to boost their exposure to microbes. Historically, we believed the dominant bacterium in the birth canal – Lactobacillus – was the first and most important microbe to seed the baby’s gut. Instead, the microbes that form the foundation of a newborn’s gut microbiome come mainly from the mother’s gut, not her vagina. This is when the baby’s head is face down facing the mother’s back, with their chin tucked down. But this system can be distruptedThis coordinated system – birth exposure, maternal gut microbes and breastmilk – has evolved to optimise babies’ survival.