how many centimeters do you have to be before your water breaks?
It begins when your cervix starts to open (dilate) and ends when it is completely open (fully dilated) at 10 centimeters. When the cervix dilates from 0 to 3 or 4 centimeters, contractions get stronger as time progresses. Mild contractions begin at 15 to 20 minutes apart and last 60 to 90 seconds.