Intrauterine Devices (IUDs)

The intrauterine device (IUD) is a small plastic device that is inserted into the uterus. An IUD's contraceptive action begins as soon as the device is placed in the uterus and stops as soon as it is removed. Precisely how the IUD prevents pregnancy is a mystery. Some experts believe that the presence of the IUD alters the fluids in the fallopian tubes and uterus, which reduces the chances for fertilization.

The intrauterine device shown uses copper as the active contraceptive, others use progesterone in a plastic device. IUDs are very effective at preventing pregnancy (less than 2% chance per year for the progesterone IUD, less than 1% chance per year for the copper IUD). IUDs come with increased risk of ectopic pregnancy and perforation of the uterus and do not protect against sexually transmitted disease. IUDs are prescribed and placed by health care providers.

IUD Forms

The two standard IUDs are copper-releasing or progestin-releasing IUDs. Both are effective and have specific advantages and disadvantages:

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Copper-Releasing IUDs. Copper-releasing IUDs (ParaGard, Nova T) are partly wrapped in copper and can remain in the uterus for 10 years. So-called frameless copper IUDs (Gynefix, FlexiGard, or CuFix) consist of nylon thread that holds the copper sleeves. They are equal to standard copper IUDs in effectiveness and may have fewer side effects. They are difficult to implant and not yet available in the US. A number of other new designs are also under investigation.