The intrauterine device and primary tubal infertility [letter].

The results of a population-based retrospective case-control study published in 1985 on the link between prior use of an IUD and primary tubal infertility have been re-analyzed. The original results set the relative risk of tubal infertility at 2.6 for ever users of an IUD but 6.8 for users of the Dalkon shield. The new calculations eliminated cases of infertility due to abnormalities verified by hysterosalpingography such as bicornuate uterus or uterine polyps; included 15 cases for whom no matched controls with the same matching criteria. The new data set included 487 of 518 potential controls for 161 cases. The new computation yielded a relative risk of 3.7 for ever-use of any IUD 3.9 for ever-use of a copper IUD 6.0 for ever-use of a Dalkon shield and 3.4 for ever-use of any IUD except the Dalkon shield. These results did not change the original interpretation of the study: that while the risks of infertility is heightened after use of the Dalkon shield it is still higher after use of any IUD for nulligravid women.