Progesterone is needed to sustain a pregnancy.
Mifepristone has been used, in combination with other medications called prostaglandins, for medical abortion since 1988 in France and China, and since the early 1990's in the United Kingdom and Sweden. It has been more recently licensed in nine other European countries and Israel. Millions of women worldwide have safely used mifepristone regimens to end their pregnancies. Mifepristone blocks the action of progesterone, which is needed to sustain a pregnancy. Misoprostol causes the uterus to contract, and helps the pregnancy tissue to pass.