Ectopic pregnancy and intrauterine contraceptive devices: new perspectives. The Women's Health Study.

In the period 1965 through 1977 the number of ectopic pregnancies in the United States tripled. A collaborative multicenter case-control study was set up to examine ectopic pregnancy as well as several other suspected complications related to use of an intrauterine contraceptive device (IUD). To determine to what extent IUD use might be related to this increase, the authors analyzed 615 women who had had an ectopic pregnancy and 3453 controls. Most important, women who had never used an IUD were equally likely to have an ectopic pregnancy as women who had used an IUD. Looking at the comparative risks for current contraceptive users, all current users, including IUD users, were less likely to have had an ectopic pregnancy than women not currently using contraceptives. Likelihood of ectopic pregnancy was the same regardless of whether a copper-containing or an inert plastic IUD was used. Among current IUD users, those who had used an IUD for a long time (25 months or more) were 2.6 times as likely to have had an ectopic pregnancy as short-term (less than 25 months) users. This difference between long- and short-term IUD users persisted for some time (not longer than 1 year) after removal of the IUD. Use of the IUD probably did not play a role in the recent tripling of ectopic pregnancies in the United States.