Contraceptive Use and the Risk of Ectopic Pregnancy: A Multi-Center Case-Control Study

OBJECTIVE: To evaluate the association between the risk of ectopic pregnancy (EP) and the use of common contraceptives during the previous and current conception/menstrual cycle. METHODS: A multi-center case-control study was conducted in Shanghai. Women diagnosed with EP were recruited as the case group (n = 2,411). Women with intrauterine pregnancy (IUP) (n = 2,416) and non-pregnant women (n = 2,419) were matched as controls at a ratio of 1∶1. Information regarding the previous and current use of contraceptives was collected. Multivariate logistic regression analyses were performed to calculate odds ratios (ORs) and the corresponding 95% confidential intervals (CIs). RESULTS: Previous use of intrauterine devices (IUDs) was associated with a slight risk of ectopic pregnancy (AOR(1) = 1.87 [95% CI: 1.48–2.37]; AOR(2) = 1.84 [1.49–2.27]), and the risk increased with the duration of previous use (P(1) for trend <10(−4), P(2) for trend <10(−4)). The current use of most contraceptives reduced the risk of both unwanted IUP (condom: AOR = 0.04 [0.03–0.05]; withdrawal method: AOR = 0.10 [0.07–0.13]; calendar rhythm method: AOR = 0.54 [0.40–0.73]; oral contraceptive pills [OCPs]: AOR = 0.03 [0.02–0.08]; levonorgestrel emergency contraception [LNG-EC]: AOR = 0.22 [0.16–0.30]; IUDs: AOR = 0.01 [0.005–0.012]; tubal sterilization: AOR = 0.01 [0.001–0.022]) and unwanted EP (condom: AOR(1) = 0.05 [0.04–0.06]; withdrawal method: AOR(1) = 0.13 [0.09–0.19]; calendar rhythm method: AOR(1) = 0.66 [0.48–0.91]; OCPs: AOR(1) = 0.14 [0.07–0.26]; IUDs: AOR(1) = 0.17 [0.13–0.22]; tubal sterilization: AOR(1) = 0.04 [0.02–0.08]). However, when contraception failed and pregnancy occurred, current use of OCPs (AOR(2) = 4.06 [1.64–10.07]), LNG-EC (AOR(2) = 4.87 [3.88–6.10]), IUDs (AOR(2) = 21.08 [13.44–33.07]), and tubal sterilization (AOR(2) = 7.68 [1.69–34.80]) increased the risk of EP compared with the non-use of contraceptives. CONCLUSION: Current use of most contraceptives reduce the risk of both IUP and EP. However, if the contraceptive method fails, the proportions of EP may be higher than those of non-users. In the case of contraceptive failure in the current cycle, EP cases should be differentiated according to current use of OCPs, LNG-EC, IUDs, and tubal sterilization. In addition, attention should be paid to women with previous long-term use of IUDs.