During childbirth, a hormone produced by the pituitary gland causes muscles of the mother's uterus (or womb) to contract. The more contractions there are, the more hormone is produced.
Oxytocin is produced during childbirth to dilate the cervix. once the cervix is at a 10, this completes stage 1 and carries on to the birth of a fetus which is stage 2. the cervix being at a 10 also helps with stage 3 which is the delivery of the placenta.
