Most women had inaccurate perceptions about the safety and effectiveness of intrauterine devices (IUDs) in preventing pregnancy, including not knowing that IUDs are more effective contraceptives than birth control pills, researchers said.
In addition, many didn't know that the devices don't increase the risk of getting a sexually transmitted disease, added researchers, whose work appeared in the journal Contraception.
"It's not clear whether women have an overly optimistic view of the effectiveness of the birth control pill or an overly pessimistic view of the IUD," said lead author Lisa Callegari, a clinical assistant professor at the University of Washington.
Whatever the source, these misperceptions lead to underuse of "one of the most safe and effective methods" of birth control, said Jeffrey Peipert, an obstetrics and gynecology professor at Washington University, who was not part of the study.
IUDs, which include the brand name products ParaGard, Mirena and now Skyla, are small plastic or copper-and-plastic objects inserted into the uterus. They can be left implanted for years, and are more than 99 percent effective at preventing pregnancy.
In contrast, the birth control pill has been found in real-world practice to be about 95 percent effective.
Callegari and her team surveyed more than 1,600 women between ages 18 and 50 who had visited one of four clinics in Pennsylvania. Five percent were currently using an IUD and another 5.8 percent had used one previously.
Only about one in five of the women correctly stated that IUDs are more effective at preventing pregnancy than the pill, and just 28 percent knew that an IUD is more cost-effective than the pill when it is used for more than three years.
The women in the study were considerably more knowledgeable about the risk of disease related to an IUD, with 57 percent answering correctly that there is no greater risk of contracting a sexually transmitted disease with an IUD compared with the pill.
Peipert noted that IUDs have a bad reputation, and so he's not surprised they might be viewed less well. Thousands of women sued the makers of one IUD sold in the 1970s because of injuries sustained from infections.
"It's not surprising, because of the history of the IUD in the United States, that people still have inaccurate perceptions of the device," said Rebecca Allen, an assistant professor of obstetrics and gynecology at Brown University, who was not involved in the study.
According to a 2012 study by the Centers for Disease Control and Prevention, 28 percent of women of reproductive age use oral contraception, followed closely by sterilization methods such as getting the fallopian tubes "tied," used by 27 percent of women.
The same study found that IUD use had risen from 0.8 percent of reproductive-age women in 1995 to 5.6 percent in 2010.
Changes in health care laws and the introduction of the first new IUD in 12 years may make more women choose IUDs.
The devices carry an often steep upfront cost ($400 to $1,000), but under the Affordable Care Act, new health plans or those that lose their grandfathered status are required to provide a range of preventive benefits, including birth control, without patient cost-sharing (though some plans may require women to pick up related expenses, such as lab charges).
The new IUD, Skyla, at left, became available in February. It is made by Bayer, the same company that makes Mirena, another IUD sold in the U.S. Unlike Mirena, which is recommended for women who have had a child, Skyla has no such restrictions (nor does ParaGard, the third type of IUD sold in the U.S.). Mirena is currently the subject of numerous lawsuits alleging some complications, such as device dislocation and expulsion.
Skyla is slightly smaller than other IUDs and is designed to protect against pregnancy for up to three years, a shorter time frame than the others, although any IUD can be removed at any time.
Reuters, The Washington Post and Kaiser Health News contributed to this report.