Pelvic inflammatory disease with intrauterine device use: a reassessment

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.