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Intrauterine Devices

by Laura Sech, Daniel R. Mishell, Jr., MD; Emily Silverstein

Intrauterine devices (IUDs) are small, flexible plastic devices that are inserted into the uterus. An IUD is left in place for 3, 5, or 10 years, depending on the type, or until the woman wants the device removed. IUDs must be inserted and removed by a doctor or other health care practitioner. Insertion takes only a few minutes. Removal is also quick and usually causes minimal discomfort. IUDs prevent pregnancy by

  • Killing or immobilizing sperm

  • Preventing sperm from fertilizing the egg

  • Creating an inflammatory reaction inside the uterus

Understanding Intrauterine Devices

Intrauterine devices (IUDs) are inserted by a doctor into a woman’s uterus through the vagina. IUDs are made of molded plastic. Two types of IUDs release a progestin called levonorgestrel. The other type is T-shaped and has a copper wire wrapped around the base and on the arms of the T. A plastic string is attached to the IUD. The string enables a woman to make sure the device is still in place and a doctor to easily remove it.

In the United States, about 5.5% of women who use contraception use IUDs. More and more women are using them because of their advantages over oral contraceptives:

  • IUDs are very effective.

  • IUDs have no general, bodywide (systemic) effects.

  • Women need to make only one contraceptive decision every 3, 5, or 10 years.

Three types of IUDs are currently available in the United States. Two of them release a progestin (levonorgestrel). One of these is effective for 3 years, and the other is effective for 5 years. During that time, only about 0.5% of women become pregnant. The third type, which contains copper, is effective for 10 years. During that time, fewer than 2% of women become pregnant. One year after removal of an IUD, 80 to 90% of women who try to conceive do so.

Most women, including those who have not had children, and adolescent girls, can use IUDs . However, IUDs should not be used when the following conditions are present:

  • A pelvic infection, such as a sexually transmitted disease or pelvic inflammatory disease

  • A structural abnormality that distorts the uterus

  • Unexplained bleeding from the vagina

  • Cancer of the cervix or the lining of the uterus (endometrium)

  • For levonorgestrel-releasing IUDs, breast cancer or an allergy to levonorgestrel

  • For copper IUDs, Wilson disease or an allergy to copper

If women are pregnant, an IUD is not inserted.

Having had a sexually transmitted disease, pelvic inflammatory disease, or a mislocated (ectopic) pregnancy in the past does not prevent women from using an IUD.

Religious beliefs that prohibit abortion do not prohibit use of IUDs because IUDs do not prevent conception by causing a fertilized egg to be aborted. However, when used for emergency contraception (see Emergency Contraception), a copper IUD may prevent a fertilized egg from becoming implanted in the uterus.

An IUD may be inserted at any time during the menstrual cycle if women have not had unprotected sex since their last period. If they have had unprotected sex, a pregnancy test must be done before an IUD is inserted, and women are advised to use another method of contraception until the test is done. Pregnancy must be ruled out before the IUD is inserted unless women wish to use an IUD as emergency contraception after unprotected sex. In such cases, a copper IUD may be inserted to prevent unwanted pregnancy. If inserted within 5 days of one act of unprotected sex, a copper IUD is nearly 100% effective as emergency contraception. Then, if the woman wishes, it may be left in place for long-term birth control. A levonorgestrel-releasing IUD is not used for emergency contraception, and pregnancy must be ruled out before it is inserted. An IUD may be inserted immediately after a miscarriage or an abortion that occurs during the 1st or 2nd trimester and immediately after the placenta is delivered after a cesarean delivery.

The uterus is briefly contaminated with bacteria at the time of insertion, but an infection rarely results. IUD strings do not provide access for bacteria. An IUD increases the risk of a pelvic infection only during the first month of use. If an infection develops, it is treated with antibiotics.

Possible problems

Bleeding and pain are the main reasons that women have an IUD removed, accounting for more than half of all removals before the usual replacement time. The copper IUD increases the amount of menstrual bleeding and may cause cramps. NSAIDs can usually relieve the cramps. The levonorgestrel-releasing IUDs reduce the amount of menstrual bleeding, and after 1 year, menstrual bleeding stops completely in about 6% of women who use the 3-year IUD and in 20% of women who use the 5-year IUD.

About 5% of IUDs are expelled during the first year after insertion, often during the first few weeks. They are more likely to be expelled if women are young or have not had children.

Sometimes a woman does not notice the expulsion. A plastic string is attached to the IUD so that a woman can check every so often, especially after a menstrual period, to make sure that the IUD is still in place. If she cannot find the string, she should use another contraceptive method until she can see her health care practitioner to determine whether the IUD is still in place. If another IUD is inserted after one has been expelled, it usually stays in place.

Rarely, the uterus is perforated during insertion. Usually, perforation does not cause symptoms. It is discovered when a woman cannot find the plastic string and ultrasonography or an x-ray shows the IUD located outside the uterus. An IUD that perforates the uterus and passes into the abdominal cavity must be surgically removed, sometimes using laparoscopy, to prevent it from injuring and scarring the intestine.

For women who conceive with an IUD in place, the likelihood of having a mislocated (ectopic) pregnancy is about 50%. Nonetheless, the overall risk of an ectopic pregnancy is much lower for women using IUDs than for those not using a contraceptive method because IUDs prevent pregnancy effectively.

Possible benefits

In addition to providing effective birth control, all types of IUDs may reduce the risk of uterine (endometrial) cancer. The 5-year levonorgestrel-releasing IUD is also effective treatment for women who have heavy menstrual cycles.

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