Objective: To evaluate the existing data to estimate the rate of ectopic pregnancy among emergency contraceptive pill treatment failures.
Data sources: Our initial reference list was generated from a 2008 Cochrane review of emergency contraception. In August 2009, we searched Biosys Previews, the Cochrane Database of Systematic Reviews, Medline, Global Health Database, Health Source: Popline, and Wanfang Data (a Chinese database).
Methods: This study included data from 136 studies, which followed a defined population of women treated one time with emergency contraceptive pills (either mifepristone or levonorgestrel) and in which the number and location of pregnancies were ascertained.
Results: Data from each article were abstracted independently by two reviewers. In the studies of mifepristone, 3 of 494 (0.6%) pregnancies were ectopic; in the levonorgestrel studies, 3 of 307 (1%) were ectopic.
Conclusion: The rate of ectopic pregnancy when treatment with emergency contraceptive pills fails does not exceed the rate observed in the general population. Because emergency contraceptive pills are effective in lowering the risk of pregnancy, their use will reduce the chance that an act of intercourse will result in ectopic pregnancy.
Level of evidence: III.