Use of copper intrauterine devices and the risk of tubal infertility amongnulligravid women

Background: Previous studies of intrauterine devices (IUDs), many of which are no longer in use, suggested that they might cause tubal infertility. Th e concern that IUDs that contain copper - currently the most commonly used type - may increase the risk of infertility in nulligravid women has limite d the use of this highly effective method of birth control. Methods: We conducted a case-control study of 1895 women recruited between 1997 and 1999. We enrolled 358 women with primary infertility who had tubal occlusion documented by hysterosalpingography, as well as 953 women with p rimary infertility who did not have tubal occlusion (infertile controls) an d 584 primigravid women (pregnant controls). We collected information on th e women's past use of contraceptives, including copper IUDs, previous sexua l relationships, and history of genital tract infections. Each woman's bloo d was tested for antibodies to Chlamydia trachomatis. We used stratified an alyses and logistic regression to assess the association between the previo us use of a copper IUD and tubal occlusion. Results: In analyses involving the women with tubal occlusion and the infer tile controls, the odds ratio for tubal occlusion associated with the previ ous use of a copper IUD was 1.0 (95 percent confidence interval, 0.6 to 1.7 ). When the primigravid women served as the controls, the corresponding odd s ratio was 0.9 (95 percent confidence interval, 0.5 to 1.6). Tubal inferti lity was not associated with the duration of IUD use, the reason for the re moval of the IUD, or the presence or absence of gynecologic problems relate d to its use. The presence of antibodies to chlamydia was associated with i nfertility. Conclusions: The previous use of a copper IUD is not associated with an inc reased risk of tubal occlusion among nulligravid women, whereas infection w ith C. trachomatis is.