Deciding about an IUD

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An intrauterine device (IUD) is a small, plastic, T-shaped device used for birth control. It is inserted into the uterus where it stays to prevent pregnancy.

Alternative names

Contraception - IUD; Birth control - IUD; Intrauterine - deciding; Mirena - deciding; ParaGard - deciding

Types of IUDs

You have choices for what type of IUD to have. Talk with your health care provider about which type may be best for you.

Copper-releasing IUDs:

  • Start working immediately after being inserted.
  • Work by releasing copper ions. These are toxic to sperm. The T-shape also blocks sperm and keeps them from reaching the egg.
  • Can stay in the uterus for up to 10 years.
  • Can also be used for emergency contraception.

Progestin-releasing IUDs:

  • Start to work within 7 days after being inserted.
  • Work by releasing progestin. Progestin is a hormone used in many kinds of birth control pills. It prevents the ovaries from releasing an egg.
  • Have a T-shape that also blocks the sperm and keeps sperm from reaching an egg.
  • Can stay in the uterus for 3 to 5 years. How long depends on the brand. There are 2 brands available in the United States: Skyla and Mirena. Mirena can also treat heavy menstrual bleeding and reduce cramps.

How IUDs work

Both types of IUDs prevent sperm from fertilizing an egg.

Progestin-releasing IUDs also works by:

  • Making the mucus around the cervix thicker, which makes it harder for sperm get inside the uterus and fertilize an egg
  • Thinning the lining of the uterus, which makes it more difficult for a fertilized egg to attach

Pros and cons

IUDs have certain benefits.

  • They are more than 99% effective at preventing pregnancy.
  • You don't need to think about birth control each time you have sex.
  • One IUD can last for 3 to 10 years. This makes it one of the cheapest forms of birth control.
  • You become fertile again almost immediately after an IUD is removed.
  • Copper-releasing IUDs do not have hormonal side effects and may help protect against uterine (endometrial) cancer.
  • Both types of IUDs may lower the risk of developing cervical cancer.

There are also downsides.

  • IUDs do not prevent sexually transmitted diseases (STDs). To avoid STDs you need to abstain from sex, be in a mutually monogamous relationship, or use condoms.
  • A provider needs to insert or remove the IUD.
  • While rare, an IUD can slip out of place and need to be removed.
  • Copper-releasing IUDs can cause cramps, longer and heavier menstrual periods, and spotting between periods.
  • Progestin-releasing IUDs can cause irregular bleeding and spotting during the first few months.
  • IUDs may increase the risk for ectopic pregnancy. But women who use IUDs have a very low risk of getting pregnant.
  • Some types of IUDs may increase the risk for benign ovarian cysts. But such cysts usually do not cause symptoms and they usually resolve on their own.

IUDs do not appear to increase the risk for pelvic infection. They also do not affect fertility or increase the risk for infertility. Once an IUD is removed, fertility is restored.

Things to think about

You may want to consider an IUD if you:

  • Want or need to avoid risks for contraceptive hormones
  • Can't take hormonal contraceptives
  • Have a heavy menstrual flow and want lighter periods (hormonal IUD only)

You should not consider an IUD if you:

  • Are at high risk for STDs
  • Have a current or recent history of pelvic infection
  • Are pregnant
  • Have abnormal Pap tests
  • Have cervical or uterine cancer
  • Have a very large or very small uterus


Intrauterine device


Jatlaoui TC, Riley HEM, Curtis KM. The safety of intrauterine devices among young women: a systematic review. Contraception. 2017;95(1):17-39 PMID: 27771475

Rivlin K, Westhoff C. Family planning. In: Lobo RA, Gershenson DM, Lentz GM, Valea FA, eds. Comprehensive Gynecology. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 13.

Schreiber CA, Barnhart K. Contraception. In: Strauss JF, Barbieri RL, eds. Yen & Jaffe's Reproductive Endocrinology. 8th ed. Elsevier; 2019:chap 36.

Winikoff B, Grossman D. Contraception. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 225.

Review Date: 
Reviewed By: 
John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.