The intrauterine device (IUD) is an effective and convenient method of contraception.

It is a small plastic device placed in the uterine cavity by a doctor. Once in place, the IUD provides immediate protection from undesired pregnancy. No further effort is required by the user for success.

Two types of IUD are available in the United States. One contains copper (Paraguard) and lasts up to 12 years. The other contains a progesterone-like hormone (Mirena) and lasts 5 years.

The most important risk associated with the use of an IUD is pelvic infection. However, modern IUDs are quite safe in women who are in mutually monogamous sexual relationships. Women who are not in such a relationship are at increased risk of sexually transmitted infection and should not use an IUD.

Other risks of the IUD include cramping and increased menstrual bleeding. The Mirena IUD was developed to address this issue. Women who use the Mirena usually have a decrease in their menstrual flow and discomfort. There is a small risk that the device can be expelled from the uterus or move into the wall of the uterus, which makes removing it difficult.

No birth control method is perfect, but the risk of pregnancy with an IUD is less than 1%. If pregnancy does occur with an IUD in place, the risk of miscarriage and ectopic pregnancy is increased. So women should seek immediate medical care if they suspect they are pregnant.