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What is An Intrauterine Device?

An intrauterine device (IUD) is anything that is placed inside the uterus (womb) to prevent pregnancy. IUDs have been used by women all over the world for thousands of years. Today, IUDs are small pieces of soft plastic shaped like the letter “T.” IUDs are placed in your uterus by a health care provider.

What Types of IUDs Are There?

There are 2 types of IUDs:

  • Copper IUDs (or ParaGard, shown in Figure 1). The copper IUD has a small copper wire wrapped around it. It can be used for up to 10 years.
  • Hormonal IUDs (or Mirena, shown in Figure 2). The hormonal IUD releases a hormone called progestin. It can be used for up to 5 years.
Figure 1.

ParaGard (copper IUD). This IUD is not shown actual size, and the threads are not shown. (Reprinted with the permission of Duramed Pharmaceuticals, Inc., a subsidiary of Barr Pharmaceuticals, Inc.)

Figure 2.

Mirena (hormonal IUD). This IUD is not shown actual size, and the threads are not shown. (Reprinted with the permission of Bayer HealthCare Pharmaceuticals.)

How Do IUDs Work?

IUDs keep sperm from joining with the egg. The hormonal IUD blocks sperm from reaching the egg by making the mucus at the cervix thicker. The copper IUD kills sperm that enter the uterus. Both IUDs change the lining of the uterus. There is no proof that these changes can keep a fertilized egg from attaching to the lining of the uterus.

How Well Do IUDs Work?

  • IUDs work almost as well as having your tubes tied.
  • If 100 women each have an IUD for 5 years, one of them will get pregnant during that 5 years.

What Are the Advantages?

  • IUDs are not permanent. Your IUD can be removed at any time. Most women get pregnant right away after the IUD is taken out.
  • IUDs are easy. You only need to check the strings from time to time to make sure that the IUD is still in place.
  • IUDs work as soon as they are placed in the uterus.
  • IUDs save money. They cost about as much as 1 year of birth control pills, but they last for 5 to 10 years. They cost much less than having your tubes tied.

What Are the Risks?

  • Some women have cramping, bleeding, or spotting when the IUD is placed in the uterus and then off and on for a few months.
  • There is a very small risk of infection in the uterus during placement.
  • Very, very rarely, the IUD can go through the uterus and into the woman's belly when it is being placed. If this happens, you will need a small surgery to remove it, but your uterus will heal well. It does not usually cause permanent damage.
  • Sometimes the uterus will push the IUD out. By checking your strings each month, you can be sure that your IUD is still in place.
  • Every once in a while, a woman with an IUD gets pregnant. If this happens, the IUD is removed and there is a chance of miscarriage.


Who Can Use an IUD?

  • Any woman of any age wanting long-term (more than 1 year) effective birth control
  • Both women who have had babies and women who have not had babies
  • Women who have had sexually transmitted infections
  • Married women, single women, and women with more than one partner

Who Should Not Use an IUD?

  • A woman with an abnormally shaped uterus or abnormal vaginal bleeding
  • A woman who has a current infection in the uterus, cervix, or vagina
  • A woman who does not like the idea of having something in her uterus or who does not want to put her fingers inside of her vagina

Which IUD Should I Choose?

The copper IUD (ParaGard; Figure 1) may be best for you if…

  • You want to avoid pregnancy for many years. ParaGard lasts up to 10 years.
  • Your periods have not been heavy or crampy in the past. You can have more cramps with the copper IUD.
  • You are not allergic to copper.
  • You cannot use hormonal contraception.

The hormonal IUD (Mirena; Figure 2) may be best for you if …

  • You want to avoid pregnancy for several years. Mirena lasts up to 5 years.
  • You have had heavy, crampy periods and would like them to be lighter or even go away.
  • You would not mind if you stopped having periods. Most women with the Mirena stop having their periods after a few months.

This page may be reproduced for non-commercial use by health care professionals to share with clients. Any other reproduction is subject to JMWH approval. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JMWH suggests that you consult your health care provider.