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Intrauterine Device (IUD)

What is an intrauterine device?

An intrauterine device (called an IUD) is a small, T-shaped device with a string attached to the end. The IUD is placed inside a woman's uterus to prevent pregnancy. The insertion can be done by your family doctor during an office visit. Once it is in place, the IUD stays in your uterus until your doctor removes it. The string on an IUD hangs down 1 to 2 inches into the vagina. This allows you to check that the IUD is in the right place and allows your doctor to remove the IUD.

How does an IUD work?

Two types of IUD are available in the United States. One type contains copper (brand name: Paragard). The other type releases a small amount of the hormone progestin (brand names: Mirena and Skyla). The copper IUD prevents sperm from reaching and fertilizing the egg. It may also change the lining of the uterus. The hormonal IUD prevents eggs from being released by the ovaries. It also makes the mucous in the cervix (opening to the uterus) thicker so that sperm can't get to the egg.

Who should not use an IUD?

You shouldn't use an IUD if you're pregnant, if you have unexplained vaginal bleeding, or if you have cancer of the cervix or uterus. You should not use the copper IUD if you are allergic to copper.

How quickly does an IUD start working after it is inserted?

The copper IUD starts working right away after it is inserted.

The hormonal IUD starts working right away if it is inserted within 7 days after the start of your period. If a hormonal IUD is inserted at any other time during your menstrual cycle, you will have to wait for 7 days for it to start working. If you have sex during this time, you should use another method of birth control (for example, a condom).

What are the advantages of an IUD?

The advantages of using an IUD include the following:

  • Prevents pregnancy very effectively
  • Keeps preventing pregnancy until it is removed
  • Can prevent pregnancy for 3 to10 years (depending on which IUD you use)
  • Is inexpensive
  • Is convenient because there is nothing you have to remember to do, such as taking the birth control pill every day
  • Can be removed by your doctor at any time
  • Has a low risk of side effects.
  • Can be used safely by a woman who is breastfeeding
  • Can't be felt by a woman or her sexual partner

What are the disadvantages of an IUD?

In rare cases, the uterus can be injured when the IUD is inserted. Side effects of all IUDs may include cramping or pain when the IUD is first inserted and spotting between periods for the first 3 to 6 months. Possible side effects of copper IUDs include heavier bleeding and stronger cramps during periods. Side effects of the hormonal IUD may include irregular periods in the first 3 to 6 months.

The IUD does not protect you from any sexually transmitted infections (STIs). To reduce the risk of getting an STI, you should also use a condom when you have sex.

How long is an IUD effective?

The copper IUD works for up to 10 years. One hormonal IUD (Mirena) lasts for up to 5 years. The other hormonal IUD (Skyla) lasts for up to 3 years. Your doctor can remove the IUD at any time if you want to get pregnant or if you no longer want to use an IUD.

How do I care for my IUD?

After your IUD is put in place, you may swim, exercise, and use tampons. Continue to have regular check-ups. Call your doctor if you miss your period or if you notice any unusual fluid or odor coming from your vagina.

Once a month, you should check for the IUD string by inserting a clean finger into your vagina. Don't tug on the string. Call your doctor if you can't feel the string or if you feel the IUD itself. Either of these could mean that the IUD is not in the right place and needs to be repositioned. If your IUD is not in the right place, it may not prevent pregnancy.


  • Appropriate Use of the Intrauterine Device by Timothy P. Canavan, M.D.( 12/01/98,