connection to the placenta
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 mothers help, the contractions eventually push the fetus out of the uterus and through the vagina. Within seconds of birth, the umbilical cord is cut. Without this connection to the placenta, the baby cannot exchange gases, so carbon dioxide quickly builds up in the babys blood. This stimulates the brain to trigger breathing, and the newborn takes its first breath. See Labor and Birth - BabyCenter Video at http://www. youtube. com/watch?v=BgZ5z6RB06c for additional information.