The process of expelling the baby and its placenta from the uterus, through the birth canal, and outside the mother's body. Labor is divided into four different stages.
1st stage: Also called the stage of dilation becaused during this stage the cervix dilates to 10 centimeters.
2nd stage: Also called the stage of expulsion. Starts when the cervix is fully dilated and lasts until the baby is totally out of the birth canal.
3rd stage: Also called the placental stage. Begins with the birth of the baby and continues until the placenta and the rest of the afterbirth have been delivered.
4th stage: Occurs after delivery and lasts 1 to 2 hours while the uterus contracts back down to reduce bleeding.