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.