HOW EFFECTIVELY DO COPPER INTRAUTERINE-DEVICES PREVENT ECTOPIC PREGNANCY

Objective. To assess the risk of ectopic pregnancy when using copper i ntrauterine devices relative to non-use of contraception and female st erilization. Design. Case-control study. Material and Methods. All cas es diagnosed with a histologically verified extrauterine pregnancy and who became spontaneously pregnant in one Norwegian county from Januar y 1, 1987 through to December 31, 1990 were eligible. Non-pregnant con trol women were chosen at random from the Norwegian Population Registr y. Eligible for study were sexually active women, from 20 to 39 years of age, and who defined themselves as fecund. Included in the final an alyses were 168 cases and 1,169 controls, who had all been previously pregnant. Statistical methods. Chi square test and unconditional logis tic regression. Results. Compared with non-users of contraception, the adjusted odds ratio (aOR) among current users of copper intrauterine devices was 0.09 (95% confidence intervals (CI); 0.06-0.13). Compared with women who were sterilized, the aOR of having an ectopic pregnancy among current copper IUD users was 1.6 (95% CI; 0.7-3.5). Conclusion. Relative to non-users of contraception, current copper IUD users had a 91% (95% CI; 87-94%) protection against ectopic pregnancy, while com pared with women who had had a tubal sterilization, current copper IUD users had a 60% non-significant increased risk of ectopic pregnancy.