Simply put, chemical abortion works by blocking key pregnancy hormones then stimulating the expulsion of the baby's remains. When a mother begins a chemical abortion, she is first given mifepristone, which blocks progesterone. This hormone is responsible for many facets of pregnancy, from the health of the uterine wall to the stimulation of the mother's body to provide nutrients to the baby. Next, the woman is given a second drug, misoprostol, which artificially stimulates strong contractions to expel the remains of the baby. About 5 percent of the time, the drug combination won’t work and a surgery is required to either end the pregnancy or remove the dead infant and placenta. The older the child, the higher the failure rate of chemical abortion.