Past contraceptive method use and risk of ectopic pregnancy

Abstract

The relationship between past contraceptive method use and risk of ectopic pregnancy has been analyzed in a case-control study conducted in Milan, Italy. Cases were 158 women with diagnosis of ectopic pregnancy confirmed by laparoscopy or laparotomy, admitted to a network of university and general hospitals of Milan. The first control group (obstetric controls) included 243 women who gave birth at term (more than 37 weeks' gestation) to healthy infants at the same hospitals where the cases had been identified. The second control group (non-obstetric controls) was a random sample of 158 women admitted to the same network of hospitals where cases had been identified for diseases other than malignant, hormonal, or gynecological in origin. A total of 37 (23%) cases, 21 (9%) obstetric and 24 (15%) non-obstetric controls reported ever IUD use. The corresponding relative risk, RR, of ectopic pregnancy was 3.5 (95% confidence interval, CI, 1.9–6.5) when obstetric and 2.4 (95% CI 1.3–4.6) when non-obstetric subjects were considered as control group. The risk of ectopic pregnancy increased with duration of IUD use: in comparison with obstetric and non-obstetric controls, the RR were 2.3 and 2.0 for users for less than 2 years and 4.3 and 2.6 for longer users. There was no clear relation between time since last IUD use and risk of ectopic pregnancy, and no evidence of a decline of risk with increasing time since stopping use. A total of 80 cases (51%), 115 obstetric (47%) and 70 non-obstetric controls (44%) were ever oral contraceptives users; these differences were not statistically significant (RR 1.1, 95% CI 0.7–1.7, in comparison with obstetric control and 1.2, 95% CI 0.8–2.0, in comparison with non-obstetric ones). Finally, 44 cases of ectopic pregnancy, 70 obstetric controls and 32 non-obstetric ones were ever users of barrier methods of contraception; in comparison with never users, the risk of ectopic pregnancy was 1.2 (95% CI 0.7–1.6) and 1.9 (95% CI 1.0–3.4) for ever users, respectively, when the comparison group was obstetric and non-obstetric controls.