How Do Intrauterine Devices Work?

IUD

An intrauterine device, or IUD, is a plastic or copper birth control device that is shaped like the letter T. It is placed in the uterus by a gynecologist as an outpatient procedure. An IUD can remain in the uterus for up to 3 to 5 years before it requires replacement. According to the Canadian Medical Association, the IUD is a good choice for women who wish to prevent pregnancy but are unable to use other forms of birth control such as oral contraceptives. These include women with high blood pressure aggravated by estrogen levels, women who smoke and women who are breastfeeding.

How It Works

There are two different types of intrauterine devices: one that is made of copper and another that is made of plastic. The copper device releases small amounts of copper over time into the uterus, creating an environment in which sperm have difficulty moving. This greatly decreases the chance that a sperm will be able to reach and fertilize an egg. The plastic device, on the other hand, releases small amounts of the hormone progestin into the uterus, which prevents a woman from ovulating. Progestin, according to Planned Parenthood, also thickens the mucus in the cervix, preventing sperm from joining with an egg in case of release. Both devices trigger what are called foreign body reactions in the uterus, changing the uterine environment. Previously, it was thought that creating a "hostile" environment in the uterus avoided pregnancy by preventing implantation of a fertilized egg; however, this has not been proven.

Effectiveness

Intrauterine devices are one of the most effective contraceptives on the market, provided they remain in place and are working properly. According to the National Institutes of Health, their failure rate is approximately 1/100, compared to 3/100 for oral contraceptives and 14/100 for condoms. It is also possible for the IUD to be dislodged during a menstrual period, which would decrease its success rate. Women who have an IUD should check regularly to ensure it is in the appropriate place, and watch for warning signs of displacement.

Warning Signs

If you have an IUD, check with your doctor in any of the following situations:

• You suspect you are pregnant.
• Your IUD has come out, or is dislodged.
• Intercourse is painful, or causes bleeding.
• Your periods are lasting longer than normal.
• You are cramping more than normal.
• You have unusual discharge or unexplained bleeding.
• You skip a period.
• You experience flulike symptoms, such as aches, chills, fever.