When a pregnant woman goes into labor, the body automatically takes steps to ensure that the baby is birthed correctly and the mother remains alive during and after the birth. There are four general stages of labor, although depending on the birth, a woman might not go through all of them.
The first stage is dilation of the cervix; since the cervix acts as the neck of the uterus, it must open and stretch to allow the baby passage. Uterine contractions begin to stretch the opening, pulling it up over the head. Contractions average four to eight hours in a normal birth and end with an average 10cm dilation.
The second stage is expulsion of the fetus, or the actual childbirth; as the cervix stretches over the baby's head, contractions in the uterus increase to push the baby out. The baby passes through the cervix, through the birth canal (vagina) and through the vulva.
The third stage is passage of the afterbirth, or the placenta and related tissues. As the umbilical cord is severed from the mother's body, the uterus continues to contract to expel the placenta and blood from the uterus, which is now bleeding from having blood vessels ripped loose by the birthing process. The attending nurse or midwife will engage in uterine fundal massage at this point, helping the excess tissue pass and allowing the uterus to fully contract, sealing off the bleeding tissue so there will be no hemorrhage or clot formation.
The fourth stage is recovery and observation, making sure the baby and mother are healthy. This stage can last anywhere from a few hours to several weeks, depending on the pregnancy and any complications. During this time, the baby is evaluated for its general well-being, and the mother is counseled and allowed to rest.