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Birth Control and the IUD (Intrauterine Device)

What Is an IUD?

An IUD, or intrauterine device, is a small, plastic, flexible, T-shaped device that is placed into a woman's uterus for birth control.

How Do IUDs Work?

There are two types of IUDs available in the United States. One type releases the hormone progestin, which causes the cervical mucus to become thicker so the sperm cannot reach the egg. The hormone also changes the lining of the uterus, so implantation of a fertilized egg cannot occur. There are two hormone IUDs available: Mirena can be used for up to 5 years and the Skyla can be implanted for up to 3 years.

The other type doesn't use hormones. It contains copper, which is slowly released into the uterine cavity. The copper stops the sperm from making it through the vagina and uterus to reach the egg, thus preventing fertilization. There is one copper IUD available, the ParaGard T380A, which can be kept in place for up to 10 years.

How Effective Is the IUD for Birth Control?

The IUD is 98%-99% effective for birth control.

How Is an IUD Used?

Once the IUD has been inserted by your doctor, you do not need to take any further steps to prevent pregnancy until it is time to replace it. How long it lasts depends on the type of IUD you receive.

Are There Side Effects Associated With IUDs?

IUDs rarely cause serious side effects when used in a monogamous relationship (having only one sex partner). Side effects include pelvic inflammatory disease, painful and heavy periods, backaches, and headaches. In some cases, the IUD can penetrate the uterus and in very rare cases, the IUD can end up outside the uterus in the pelvis. Discuss these side effects with your doctor.

Mirena is actually associated with lighter menstrual periods.

Do IUDs Protect Against Sexually Transmitted Diseases?

No. IUDs do not protect against sexually transmitted diseases (STDs), including HIV (the virus that causes AIDS). The male condom provides the best protection from most STDs.

WebMD Medical Reference

Reviewed by Traci C. Johnson, MD, FACOG on January 14, 2015
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