Pelvic inflammatory disease and the intrauterine device: a causal relationship?

Abstract

IUD use in the U.S. has been declining in the past 5 years partly because of the adverse publicity given to the increased risk of pelvic inflammatory disease (PID) of IUD users. In 1977, the U.S. Food and Drug Administration recommended, on the basis of results from epidemiologic studies, that IUD labeling include the statement that "IUD use is associated with a 3-5 fold increase in infection rate." A review of the major results and some of the features of epidemiologic studies in which the contraceptive practices of PID cases were compared with controls (those without PID) showed that there is indeed an increased risk of PID among IUD users. The studies, except that of Vessey et al. however, do not provide any estimate of the magnitude of increased risk of PID to the IUD users nor ascertain whether there is a cause-and-effect relationship between IUD use and PID. Vessey found that the increased incidence of PID among IUD users was only 1.65/1000 woman-years and when compared with nonusers, the IUD user was at a 3.5-fold increased risk of PID. There is yet no evidence that any one type of IUD is associated with a higher rate of PID. Overall, although available evidence suggests that there is an increased risk of PID among IUD users compared to nonusers, the magnitude of the risk is small. It is possible that a woman's lifestyle has a greater influence on the risk of PID than the IUD per se.