The reasons for premature labour are often unknown. Premature labour usually starts by itself.
There's a greater risk if you've had a premature (preterm) baby or a late miscarriage before, or if you've had a multiple pregnancy such as twins.
Sometimes a premature birth is planned because of concerns about the health of you or your baby. If your doctors decide that your baby needs to be born early, your labour will be induced or your baby will be born by caesarean section.