Intrauterine Device

Types of IUD

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

  1. Mirena Intrauterine System (hormonal)
  2. Progestasert IUD (hormonal) *discontinued in 2001
  3. ParaGard Copper T IUD (hormone-free)

Hormonal IUDs: 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. This type of IUD also affects the lining of the uterus to prevent a fertilized egg from being implanted, should fertilization occur. Progestasert IUD must be replaced every 8-24 months. Since this IUD was discontinued in 2001, any woman who had one implanted should have had it removed by now. The Mirena IUS is the next generation of hormonal IUDs and can be used for up to five years. More about the Mirena IUS...

Non-hormonal IUDs: 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 ten years. More about the ParaGard Copper IUD...

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. Unlike regular hormonal contraceptives, IUDs do not prevent ovulation.

The very high effectiveness rates advertised for all types of IUDs are only possible with perfect use. This means that the IUD is correctly in place, with its string hanging just outside the opening of the cervix. Many IUD users never check the placement of the string, and could have expelled the IUD without knowing it. This, of course, would result in a higher pregnancy risk for these women compared to those who follow all the instructions. Expulsion of an IUD, especially in the first few weeks of use, is not an uncommon problem. The IUD is less effective for teens than for women over 20.

The IUD carries with it a number of potentially serious health risks. 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. The IUD is sometimes used as a method of emergency contraception 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. Likewise, a woman with a very large uterus would also be unsuitable. The IUD should never be used by women with multiple sex partners, due to the increased chance of contracting pelvic-inflammatory disease (PID). IUDs should not be used by any woman with PID or who has had PID in the past, or a life-threatening condition may develop. They should not be used by women with a prior ectopic pregnancy. IUDs do not offer any protection against sexually transmitted diseases.

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Related Articles

About the ParaGard Copper IUD

About the Mirena IUS

Frequently Asked Questions about the Pill and Other Hormonal Methods

List of Contraceptives

Mirena vs Paragard

Non Hormonal Contraceptives

Side Effects of Copper T


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