Not only that, it actually also releases a fourth hormone at the end of the pregnancy. So towards the end of the pregnancy, the placenta also releases a hormone known as the corticotropic releasing hormone or CRH. Now, what the corticotropic releasing hormone does is it goes on to the pituitary gland found in the brain and it stimulates the pituitary gland to release a hormone known as ACTH. And ACTH goes down to the adrenal gland and it causes the adrenal gland to produce the precursor molecule that then goes down into the placenta. And the placenta uses that precursor molecule to form even more estrogen. And the rising level of estrogen ultimately causes the contraction of the smooth muscle found inside the uterus and that eventually leads to the process of childbirth.