Your waters break when the sack that your baby has been held in breaks and the amniotic fluid drains out through your vagina. You might notice a little trickle or it could be a big gush of water that you can't control.
Despite what many people think, your waters normally break when you are in labour, rather than at the start. If your waters do break before you go into labour, call your midwife or the hospital for advice because your baby won't be protected anymore and will be at risk of infection.
The amniotic fluid should be clear and a pale straw colour, it might have a little bit of blood in it. If it smells strange or if there's lots of blood, call the hospital.