The term "abortion" actually refers to any premature expulsion of a human fetus, whether naturally spontaneous, as in a miscarriage, or artificially induced, as in a surgical or chemical abortion. Today, the most common usage of the term "abortion" applies to artificially induced abortion.
In 1973, the Supreme Court handed down its Roe v. Wade and Doe v. Bolton decisions legalizing abortion in all 50 states during all nine months of pregnancy, for any reason, medical, social, or otherwise.
The vast majority of all abortions performed today are done for social, not medical reasons -- because a woman doesn’t feel ready for a baby at the time, because her partner wants her to have an abortion, etc. Approximately 93% of all induced abortions are done for elective, non-medical reasons such as these.
Abortion ends a pregnancy by destroying and removing the developing child. That baby’s heart has already begun to beat by the time the mother misses her period and begins to wonder if she might be pregnant (about 31 days after the mother’s last menstrual period or LMP). Surgical abortions are usually not performed before seven weeks, or 49 days LMP. By that time, the baby has identifiable arms and legs (day 45) and displays measurable brain waves (about 40 days). During the seventh through the tenth weeks, when the majority of abortions are performed, fingers and genitals appear and the child’s face is recognizably human.
This information is taken from the National Right to Life website.
The W's of Abortion