Article updated and reviewed by Bryan R. Hecht, MD, Head of The Cleveland Clinic's Youngstown (OH) Fertility Practice. Editorial review provided by VeriMed Healthcare Network on May 19, 2005.

RU-486, or mifepristone (sold as Mifeprex in the US), is a synthetic hormone currently used in over 20 countries to induce abortion in the first several weeks of pregnancy. It was approved for use in the U.S. in 2000.

Definition of Abortion

“Abortion” is the term used by doctors to describe any pregnancy that ends before 20 weeks. There are two types of abortions, spontaneous and induced.

Spontaneous abortion is defined as a pregnancy that terminates (naturally, not artificially) before the 20th completed week of gestation.

Induced abortion is the deliberate termination of pregnancy. Induced abortions can be performed surgically or can be drug-induced, which is known as “medical abortion.” Both surgical and medical methods of abortion are very effective and serious complications are rare, but the earlier in pregnancy the abortion is performed, the safer it is for the mother. RU-486 has now been used safely by millions of women around the world.


RU-486 blocks the action of the natural hormone progesterone, which is essential to maintain a pregnancy. RU-486 is given orally, usually followed by a second medication, misoprostol (Cytotec), which is given one to three days later to stimulate uterine contractions. This drug combination is the most predictable and widely used medical abortion regimen currently in use. Medical abortion is usually used before the first seven to nine weeks of pregnancy (counting from the last menstrual period). Although dosage regimens vary, this type of medical abortion is about 95% effective. In rare cases, the method fails to cause abortion, and a follow-up surgical abortion procedure is required.

There are no apparent long-term adverse health effects from RU-486 and it is not known to have an adverse effect on a woman’s future fertility. In addition to the bleeding and uterine cramping that normally accompany the abortion, other side effects may include nausea, vomiting, diarrhea, fever, or chills. Ibuprofen or a mild oral narcotic may be prescribed for the cramping. Patients should contact their physician immediately if using RU-486 and wind up experiencing the following problems: very heavy vaginal bleeding, a sustained fever, or NO bleeding within 24 hours of taking the misoprostol. Patients should see the physician again within one to two weeks of taking RU-486 to ensure that a complete abortion has occurred.

Approximately 2% of all pregnancies are ectopic, meaning that the pregnancy is lodged in one of the fallopian tubes instead of in the uterus. The mifepristone/misoprostol regimen will not reliably terminate an ectopic pregnancy. If such a patient receives RU-486, the ectopic pregnancy can continue to grow until it ruptures the tube, potentially causing dangerous internal bleeding. This is why it is important for the patient to notify the physician if vaginal bleeding does NOT occur after administration of the medications.

There are advantages and disadvantages to medical versus surgical abortion. The primary advantages of medical abortion include avoiding an invasive surgical procedure and anesthesia, more privacy, and a greater sense of personal control over the experience. Patients should consider and discuss their feelings and opinions about medical versus surgical abortion with their physician.