Pelvic inflammatory disease with intrauterine device use: a reassessment

Abstract

This reassessment of IUDs as a risk factor for PID contrasts study results from prospective and case-control studies. Except for a transient increased risk after IUD insertions, increased risk is seen mainly in case-control studies after 1973, the time of a major PID epidemic and adverse publicity related to the Dalkon Shield. Removal of oral contraceptive users from case-control studies generally reduces their reported odds ratios, frequently to borderline statistical significance for studies with high accuracy of PID diagnosis. The remaining elevated odds ratios likely relate to diagnostic bias as primary care clinicians are more likely to refer patients wearing an IUD to referral centers where case-control studies are conducted. Biased case-control studies provided evidence for expensive litigation, resulting in removal of IUDs from the American market. The Food and Drug Administration requirements for postmarketing surveillance are inadequate to provide prospective data to avoid this kind of loss.A reassessment of the relation between IUD use and pelvic inflammatory disease (PID) suggests that the correlation may not be supported by prospective cohort studies. The increased risk of pelvic inflammatory disease associated with IUD use was based primarily on case control studies after 1973, at which time there was a major PID epidemic and adverse publicity about the Dalkon Shield. Because case control studies may have been biased, these studies should not form the basis for the current consensus that IUD use increases the risk of PID. Problems with case-control studies include inaccuracy of PID diagnosis, the removal of oral contraceptive users from such studies, and miscalculations about the relative risk of PID. Another important factor is the increased incidence of sexually transmitted disease. These factors contributed to the current teaching in medical schools that IUD use increases the risk of PID. Although there is a small increased risk of PID in IUD users, due primarily to contamination of the uterine cavity during insertion, the risk is low. A comparison of case-control studies with prospective cohort studies does not support the association between IUD use and PID, and this should be considered when recommendations are made to physicians from developing countries. The potential of such instruction in influencing family planning policy decisions could have serious consequences for developing countries.