Signs that labour has begun
You’re likely to recognise the signs of labour when the time comes, but if you’re in any doubt, don't hesitate to contact your midwife.
Other signs that labour is beginning include your waters breaking (rupture of the membranes),
backache and an urge to go to the toilet, which is caused by your baby’s head pressing on your bowel.
Follow this link to NHS Inform for more details.
Also there is a short film here link on NHS Choices