During the pregnancy, the female hormone progesterone plays a key role in the survival of the developing child. It causes the wall of the uterus to thicken and swell with blood vessels that are then used to provide nourishment to the fertilized egg that implants itself into the uterine wall.
Secondly, progesterone inhibits the normal muscular contractions of the uterine wall. These contractions are the monthly cramping women experience that is designed to rid the uterus of the extra lining and blood supply. Without the progesterone to reduce the cramping, the fertilized egg would most likely be shed with the rest of the uterine material.
In 1980, the French pharmaceutical company of Roussel Uclaf developed a pill designed to chemically induce an abortion within the first 49 days of pregnancy. The Roussel lab which developed the pill, had used the designation of 38486 for it during its research and trials. When the pill was released on the market, it was known as RU486 (RU for Roussel Uclaf and 486 short for 38486).
RU486 is an artificial steroid that blocks the effects of progesterone on the uterus. When taken after a fertilized egg has implanted itself into the rich uterine wall, the RU486 blocks any further effects of the progesterone. This causes the developing child to literally die from starvation and/or asphyxiation. Death can occur as fast as several hours if RU486 is accompanied by other drugs, or it can take days and weeks if taken alone. In the majority of cases, the child dies a very slow and agonize death. Additionally, the RU486 counters the anti-cramping effects of the progesterone, allowing the uterus to contract and expel the dead baby.