The checkered history and bright future of intrauterine contraception in the United States.

No method of contraception stirs quite as much heated discussion and debate as the IUD. The reasons the IUD has this distinction are simple: People's opinions have been shaped by a body of seemingly discrepant (and sometimes mythical) evidence, and the issues this evidence addresses are fundamental. How does the IUD prevent pregnan-cy? What is the true relationship of IUD use to pelvic in-flammatory disease (PID) and infertility, and how does exposure to sexually transmitted bacteria modify or confound that relationship? Clinical research conducted over the past 30 years provides clues to help resolve these important issues, yet the debates over the IUD's safety 1 and mechanism of action 2 continue to rage, and misperceptions abound. Some people , for example, believe that because the IUD rests in the uterus, it must be aborting early pregnancies. Others reason that PID and infertility that appear any time during or after use of an IUD are sure to have been caused by the in-vasive procedure. Still others believe that the IUD (like other foreign objects) lowers the body's natural defenses and facilitates the development of PID and infertility among women exposed to sexually transmitted bacteria. Even weak research that supports these arguments can appear to make the claims irrefutable. Research that generates results counter to these assumptions has to be flawless, unchallengeable and repeated to have any lasting impact. Thus, although the most recent research has shown these assumptions to be unwarranted, the controversy continues. BACKGROUND The IUD was once a popular form of birth control in the United States: In the 1970s, nearly 10% of women who practiced contraception relied on the device; 3 today, fewer than 1% do. 4 The sharp drop in IUD use resulted from a combination of interrelated factors and events. The five most important factors were the following: • the published account of cases of septic maternal death among women who became pregnant while using the Dalkon Shield; 5 • the discovery that the Dalkon Shield was associated with an increased risk of PID; 6 • the scientific, legal, governmental and media actions that unfolded to bring the Dalkon Shield manufacturer to declare bankruptcy and recall all devices; • the business decisions that led other manufacturers to voluntarily withdraw their IUDs from the U.S. market; and • the published research that linked IUD use and infertility. 7