While most contraceptive methods reduce the risk of intrauterine pregnancy and ectopic pregnancy, for women who experience contraceptive failure, the risk of ectopic pregnancy may be greater than for women who do not use contraception. In a study published in PLOS One, 2,411 women who experienced ectopic pregnancy were matched with 2416 intrauterine pregnancy controls and 2,419 non-pregnant controls to evaluate the relationship between contraceptive use and ectopic pregnancy risk. Women were considered contraceptive users if they used one of the following methods of contraception: condoms, withdrawal, calendar rhythm method, emergency contraceptive (at least once), intrauterine device (IUD), oral contraceptive pills (OCP), or tubal sterilization for at least one menstrual cycle; current users were those who used the method in the current cycle while previous users were those who used the method in previous cycles.
Based on the analysis, the authors concluded that current use of most contraceptive methods reduced the risk of both intrauterine pregnancies and ectopic pregnancies; however, when the contraceptive method failed and pregnancy occurred, current use of oral contraceptives, levonorgestrel emergency contraception, IUDs, and tubal sterilization increased the risk of ectopic pregnancy in women vs. those who did not use contraceptives. Previous use of IUDs was linked to a slight risk of ectopic pregnancy, with this risk increasing based on duration of previous use; no increase in risk was seen in previous users of OCPs.