Friends of mine who are young enough to need birth control but old enough to remember the notorious Dalkon Shield—a contraceptive intrauterine device (IUD) linked to pelvic inflammatory disease and infertility—are still leery of IUDs. If you share their concerns, you’re hardly alone. Fewer than 6% of US women who use contraception choose IUDs. But: Many experts are urging women to take a fresh look, because today’s IUDs are among the safest, most effective and most economical forms of reversible birth control.

An IUD is a plastic, T-shaped device that a physician places in a woman’s uterus. Two brands are on the market…

  • Mirena. This device releases the hormone progestin, which thickens the cervical mucus and blocks the sperm from getting into the uterus. Major bonuses for women with heavy periods: Mirena reduces menstrual bleeding (and may even halt it) and lowers the risk for anemia and endometriosis. Mirena can be left in place for five years and costs about $800 to $1,000.
  • ParaGard. This IUD releases a tiny amount of copper that interferes with the sperm’s movement and ability to fertilize an egg. ParaGard does not lighten heavy periods—it may even increase flow and cramping at first (so women with heavy periods may prefer Mirena). Advantage: It can be left in for 10 years. ParaGard costs about $600.

I contacted Anita L. Nelson, MD, a professor of obstetrics and gynecology at the David Geffen School of Medicine at the University of California, Los Angeles, to discuss these devices and their benefits. Today’s IUDs…

  • Have very low failure rates. “IUDs are in the top tier of contraceptive protection and are as effective as sterilization,” Dr. Nelson said, adding that in the first year of use, less than 1% of IUD users will wind up pregnant. Comparison: About 6% of users of the Depo-Provera injection, 9% of users of the Pill and 17% of condom users wind up pregnant each year, given that these methods are not always used correctly.
  • Are reversible. An IUD can be removed by a physician at any time. After that, Dr. Nelson said, a woman’s fertility level immediately goes back what it would have been had she not used the IUD.
  • Are hassle-free. Once the device is inserted, all the woman has to do is reach a finger into her vagina once a month to feel for the little tail string that signals that the IUD is still in place. Unlike with certain other birth control methods, there is no need to interrupt the action prior to lovemaking.
  • Are economical—particularly considering how many years an IUD lasts. Many health insurance policies cover the cost.
  • Protect against cancer. IUDs reduce the risk for endometrial cancer…and a recent study from Spain suggests that they may cut cervical cancer risk in half.

Is it safe? Dr. Nelson said that there is a critical difference between the old-style IUD and those used today. The Dalkon Shield’s tail string had a design that may have allowed it to convey bacteria from the vagina into the uterus…whereas today’s IUDs have “monofilament” tail strings that do not facilitate movement of bacteria. About one in 1,000 women experience problems during the placement procedure (such as puncture of the uterus). Some IUD users develop ovarian cysts, which generally are harmless but sometimes can cause pain. In some cases, a woman loses her IUD early if her uterus pushes it out. Such expulsions most often occur within the first months after insertion.

In the past, the IUD was often considered most appropriate for women who had previously given birth because they are less likely to expel the device. But The American College of Obstetricians and Gynecologists (ACOG) recently declared IUDs safe for most women of childbearing age, including those who have never given birth…those with a history of ectopic (tubal) pregnancy…and teens. In addition, ACOG now says that an IUD can be placed right after childbirth, miscarriage or a D&C, rather than delaying four to six weeks as traditionally has been advised. The device does have to fit correctly, however, so women with large fibroids, uterine cancer or infections are not candidates for the IUD, Dr. Nelson said.

If you decide to get an IUD: Placement of the device takes just a few minutes and is done in a doctor’s office. You may be advised to take an over-the-counter nonsteroidal anti-inflammatory (not aspirin) beforehand to minimize discomfort during and after the insertion. Expect mild cramping and perhaps spotting or bleeding that persists for several weeks. After about five to 10 weeks, you return for a checkup.

Thereafter, you don’t need any extra monitoring outside of your normal gynecological checkups. There are no limitations on your activities. But do contact your physician if, at any time during your IUD use, you are concerned that…

  • You might have a pelvic infection. Possible warning signs include vaginal discharge, abnormal pelvic pain and/or fever.
  • You are losing your IUD (possible symptoms include heavy bleeding and cramping) .
  • You could be pregnant.

I had one final question for Dr. Nelson: Can the woman or her partner feel the IUD during sex? She told me that neither partner can feel the device itself because it is inside the woman’s uterus…and the tail string tucks away and should not be bothersome.