About 1 in 10 of us are born prematurely or pre-term, defined by The Ministry of Health as anything under 37 weeks' gestation.
Being born before your due date can be bad for your health, with higher rates of infections, breathing and feeding problems, a greater risk of neonatal death, and other problems that linger into adult life.
So the idea of an early warning system for mothers at risk of giving birth early could be a powerful tool.
The key looks like it could be found in our microbes. Professor David A. Relman from the Department of Medicine and the Department of Microbiology & Immunology at Stanford University is studying the colonies of bacteria living inside an expectant mother in the early stages of pregnancy.