In the United States, abortion is used most often to end an unplanned pregnancy. Unplanned pregnancies happen when birth control is not used, is used incorrectly or fails to prevent a pregnancy. Abortion is also used to end a pregnancy when tests reveal that the fetus is abnormal. Therapeutic abortion refers to an abortion recommended when the mother's health is at risk.
Roughly one-half of all abortions are done during the first 8 weeks of pregnancy and about 88% during the first 12 weeks of pregnancy.