If you have a gush of fluid from the vagina, your waters may have broken.

http://www.patient.co.uk/health/pelvic-pain-in-women

This is the mucous plug from the neck of the womb. If you have a gush of fluid from the vagina, your waters may have broken. You should contact your midwife immediately. If you have pelvic pains that come and go in a regular pattern, contact your midwife for advice.