 Step one, at the abortion facility or at home, the woman swallows Mephepristone pills. Mephepristone blocks the action of a hormone called progesterone. Progesterone is naturally produced in the mother's body to stabilize the lining of the uterus. When Mephepristone blocks progesterone, the lining of the mother's uterus breaks down, cutting off oxygen and vital nutrients to the embryo, who then dies inside the mother's womb.