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 24, and the third trimester lasts from the 25th 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. A variety of drug-based abortion methods may be carried out under a physician’s supervision. In a method commonly referred to as the morning-after pill, a woman is given large doses of estrogen a female hormone within 72 hours of unprotected sexual intercourse and again 12 hours later. This high dose halts fetal development at the earliest stages after conception, or the point when a man’s sperm fertilizes a woman’s egg. Typical side effects of the morning-after pill may include nausea, headache, dizziness, breast tenderness, and fluid retention. Within the first seven weeks of pregnancy, a combination of two drugs can be given in pill form to abort a fetus. A pregnant woman first takes the drug mifepristone, known as RU-486, which blocks progesterone, a hormone needed to maintain the pregnancy. About 48 hours later, she takes another drug called misoprostol. Misoprostol is a prostaglandin (a hormone-like chemical produced by the body) that causes contractions of the uterus, the organ in which the fetus develops. These uterine contractions expel the fetus. Misoprostol can also induce abortion when taken with methotrexate, an anticancer drug that interferes with cell division. A physician first injects a pregnant woman with methotrexate. About a week later, the woman takes misoprostol to induce uterine contractions and expel the fetus. Both of these drug combinations effectively end pregnancy in 95 percent of the women who take them. Some women experience nausea, cramping, and bleeding. The most serious complications, such as arrhythmia, edema, and pneumonia, affect the heart and lungs and may cause death. In two procedures known as preemptive abortion and early uterine evacuation, a narrow tube called a canola is inserted through the cervix (the opening to the uterus) into the uterus. The canola is attached to a suction device, such as a syringe, and the contents of the uterus, including the fetus, are extracted. Preemptive abortion uses a smaller canola and is performed in the first four to six weeks of pregnancy; early uterine evacuation, which uses a slightly larger canola, is performed in the first six to eight weeks of pregnancy. Both types of abortions typically require no anesthesia and can be performed in a clinic or physician’s office. The entire procedure lasts for only several minutes. In preemptive abortions the most common complication is infection. Women who undergo early uterine evacuation may experience heavy bleeding for the first few days after the procedure.