Flexi Says: Near the time of birth, the amniotic sac breaks in a gush of fluid. Often when this occurs, women say that their "water broke." Labor usually begins within a day of this event. Labor involves contractions of the muscular walls of the uterus, which cause the cervix to dilate. With the mother’s help, the contractions eventually push the fetus out of the uterus and through the vagina. After birth, the umbilical cord is cut