Induced abortions are performed using drugs or surgery. The safest and most appropriate method is determined by the age of the fetus, which is calculated from the beginning of the pregnant woman's last menstrual period.
Most pregnancies last an average of 39 to 40 weeks. This period is divided into three stages known as trimesters. The first trimester consists of the first 13 weeks, the second trimester spans weeks 14 to 28, and the third trimester lasts from the 29th week to birth. Abortions in the first trimester of pregnancy are easier and safer to perform while abortions in the second and third trimesters require more complicated procedures and pose greater risks to a woman's health. In the United States, a pregnant woman's risk of death from a first-term abortion is less than 1 in 100,000. The risk increases by about 30 percent with each week of pregnancy after 12 weeks.
Medical abortion may be an alternative to surgical abortion for some women seeking to terminate their pregnancies during the first trimester. Currently, there are two combinations of drugs that are most commonly used. The first is mifepristone, an antiprogestin that is distributed in Europe under the name RU-486, coupled with the prostaglandin misoprostol, an ulcer medicine marketed in the United States as Cytotec. The second method utilizes methotrexate, a drug also used to treat some cancers, arthritis, and psoriasis, as well as ectopic pregnancies. It, too, is combined with misoprostol for medical abortion.