Labor Department

Birth is an incredible process directed by hormones and carried out by your organs. Typically, childbirth is kicked off by stress -- at the end of gestation, baby is running out of room and wants to get out. Corticotropin-releasing hormones and cortisol from baby's adrenal glands send an evacuation notice to mom's body: "GET ME OUTTA HERE!" The cortisol then pumps up estriol, a type of estrogen present during pregnancy. Estriol slows down progesterone made by placenta and helps co-ordinate uterine contractions. As estrogen starts contractions, the uterus makes prostaglandins, which also force progesterone levels down. Prostaglandins also make you poop and, along with the hormone relaxin (yes, this is a real, actual hormone name) from the ovaries, get the cervix to soften and dilate to let baby through to the vaginal canal. And that's just the beginning!