Epigee Birth Control Guide
Intrauterine Device
Mirena Intrauterine SystemProgestasertParaGuard Copper T

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The intrauterine device, or IUD, is a small plastic or metal device that is placed inside the uterus by a doctor for an extended length of time. There are three types of IUDs available today in the US:

  1. Mirena intrauterine System (hormonal)
  2. Progestasert IUD (hormonal)
  3. ParaGuard Copper T IUD (hormone-free)

plastic Mirena IUD Hormonal IUDs prevent pregnancy by releasing the hormone progestin, which thickens the cervical mucus, acting as a barrier to prevent sperm from entering the uterus. They also affect the lining of the uterus to prevent a fertilized egg from being implanted, should fertilization occur. Because of the hormonal component, these type of IUDs must be replaced every 8-24 months, depending on the brand. (See box on Oral Contraceptives page for more about how hormones act as birth control.)

For copper IUDs, the metal itself seems to exert a spermicidal effect. The copper also affects the lining of the uterus by not allowing a fertilized egg to implant, and it stimulates the production of prostaglandins, chemicals that affect the hormones needed to support a pregnancy. ParaGard is a long-term IUD that may be left in place for 8 years.

All mechanisms of the IUD are not completely understood. The IUD may also cause inflammation of the uterus, preventing implantation of an embryo and making it more difficult for sperm to enter.

The IUD carries with it a number of serious health risks, which caused many manufacturers in the past to stop distribution, although newer IUDs are thought to be safer. Health risks include pelvic-inflammatory disease, permanent infertility, ectopic pregnancy, and even death. Common side effects include irregular periods as well as side-effects common to oral contraceptives for IUDs treated with hormones. In women who do begin healthy pregnancies while using the IUD, the device causes a miscarriage half of the time. IUDs may also be used as a method of Emergency Contraceptive treatment after unprotected intercourse.

Because of the risks to fertility, doctors do not usually recommend the IUD to women who have not had children. A woman's uterus is smaller if she has not carried a pregnancy to full term, and a smaller uterus poses greater risk for irritation from the IUD and subsequent infection of the uterus. The IUD should never be used by women with multiple sex partners, due to the increased chance of contracting pelvic-inflammatory disease (PID). IUDs do not offer any protection against sexually transmitted diseases.

Image Credit: from Contraceptive Technology, RA Hatcher, et al., 1998

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   Visitors Since 04-15-03

 Updated: Apr. 15, 2003

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