How does an Abortion Pill work? Both abortion pills, mifepristone and misoprostol, are usually used in order to terminate a pregnancy. Mifepristone causes the embryo to detach from the uterus thereby cutting off essential nutrients and oxygen carried by the blood. Misoprostol is then taken two days later and triggers the evacuation of the embryo remnants through the vagina. This often appears as a heavy period.