Abortion, in its most common usage, refers to the voluntary, or induced, termination of pregnancy, generally through the use of surgical procedures or drugs. As a result, birth does not take place. Medically, the term also refers to the early termination of a pregnancy by natural causes ("spontaneous abortion" or miscarriage), which ends one in five of all pregnancies, usually within the first thirteen weeks, or to the cessation of normal growth of a body part or organ.