In order to decide whether you are a good candidate for an IUD, you need to know:
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How IUDs work
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How effective they are
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Who should avoid them
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What their advantages are
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Whether you can tolerate possible side effects and complications
How do IUDs Work?
Scientists aren't sure why the IUD is such an effective method of birth control. It was once thought that, as foreign objects, they produced an inflammatory response in the uterus that disrupted the implantation of a fertilized egg, but researchers haven't been able to prove this theory. In fact, when they look for fertilized eggs in the fallopian tubes of IUD users, they rarely find them. These studies should help ease the minds of women who are opposed to methods which prevent pregnancy by aborting a fertilized egg.
Now more researchers are fairly certain that IUDs are spermicidal. The inflammatory response may be enough to kill sperm before they ever get into the fallopian tubes to fertilize an egg.
The three IUDs currently available in the United States both have added pregnancy-preventing characteristics. The Copper-T 380A, or ParaGard, is a T-shaped device with copper wire wound around the stem and copper tubing on the arms of the T. The frame also contains barium sulfate so that the IUD will show up on x-rays. The copper, besides intensifying the inflammatory response, has a chemical impact on the uterine lining, changing the normal levels of several enzymes. The environment copper creates throughout the reproductive tract is not friendly to eggs and sperm, making it unlikely that they will ever come together and form an embryo. The ParaGard remains effective for up to 10 years.
The Progestasert IUD is also T-shaped, but the vertical stem is actually a reservoir for 38 milligrams of progesterone, the naturally occurring hormone that helps bring about menstruation. Like Norplant implants or Depo-Provera (see "Hormonal Options: Pills, Shots, and Implants") the device releases progesterone daily. This thickens cervical mucus, making it difficult for sperm to pass through the cervix. This IUD also diminishes cramping and blood loss, so it is an excellent choice for women who have heavy, uncomfortable periods. The Progestasert remains effective as long as it contains a sufficient amount of hormone; doctors usually replace it every year.
The Mirena IUD consists of a polyethylene T-shaped body, surrounded by a sleeve, which releases a low daily dosage of the progesterone-like hormone levonorgestrel. The action of the hormone-releasing system thins the lining of the uterus, inhibits sperm movement, and thickens the cervical mucus, resulting in excellent birth control. The Mirena IUD is designed to prevent pregnancy for five years; once it is removed, fertility rapidly returns to pre-insertion status.
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The Options Today
Three IUDs are now available in the United States: the Copper-T (ParaGard), the Progestasert, and the Mirena. Over the long run, the Mirena is the single most effective reversible contraceptive available in the world today, followed closely by the Copper-T. Over seven years of wear, the cumulative probability of pregnancy is 1.1 percent for the Mirena, followed by the Copper-T at 1.7 percent. The failure rate for the Progestasert is slightly higher, but still less than the rate among typical users of the Pill. |
