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Update on Emergency Contraception

(Published March 2011)

Impact of EC on Unintended Pregnancy: Population Level

No published study has demonstrated that increasing access to emergency contraception pills (ECPs) reduces pregnancy or abortion rates at the population level,1-3 although one demonstration project4 and three clinical trials2,5,6 were specifically designed to address this issue. One explanation for this result is that even when provided with ECPs in advance of need, most women use ECPs too rarely after risky incidents to result in a substantial population effect.

In a trial conducted in San Francisco, 45% of women in the advance-provision group who had unprotected intercourse during the study period did not use ECPs.5 In a Chinese trial, 30 women in the advance-provision group (n = 746) did not use ECPs in the cycle in which they became pregnant.6 In a Nevada/North Carolina trial, 33% of women in the advance-provision group had unprotected intercourse at least once without using ECPs and 57 did not use ECPs in the cycle in which they became pregnant.2

In a demonstration project, 27 women with advance supplies of emergency contraception (EC) who became pregnant never used ECPs.4 In a Nevada/North Carolina trial, increased access to EC had a greater impact on use of ECPs among women who were at lower baseline risk of pregnancy.7 This may explain in part why increased access to EC has increased use of EC without a measurable effect on pregnancy rates in clinical trials.

Thus, although considerable evidence shows that ECPs are effective, several lessons can be learned from the lack of reduction in pregnancies. Women often underestimate their risk of pregnancy, and education is needed to encourage women to use ECPs every time they are needed. Over-the-counter (OTC) access is necessary but probably will not reduce unintended pregnancies sufficiently. Unless ECPs are used more frequently, and when needed, a major public health impact is unlikely.1

Although the effect of EC on unintended pregnancy rates for the overall population remains to be shown, EC is most certainly of benefit to individual women seeking to prevent an unintended pregnancy after unprotected intercourse has occurred. Women who recognize their pregnancy risk are likely to seek EC if they are aware of it, and if EC is easily accessible.

References:

  1. Raymond EG, Trussell J, Polis C. Population effect of increased access to emergency contraceptive pills: a systematic review. Obstet Gynecol. 2007;109:1818.
  2. Polis CB, Schaffer K, Blanchard K, et al. Advance provision of emergency contraception for pregnancy prevention (full review). Cochrane Database Syst Rev. 2007;2:CD005497
  3. Polis CB, Grimes DA, Schaffer K, Blanchard K, Glasier A, Harper CC,. Advance provision of emergency contraception for pregnancy prevention (full review). Cochrane Database Syst Rev. 2010, Issue 3.
  4. Glasier A, Fairhurst K, Wyke S, et al. Advanced provision of emergency contraception does not reduce abortion rates. Contraception. 2004;69:3616.
  5. Walsh TL, Frezieres RG. Patterns of emergency contraception use by age and ethnicity from a randomized trial comparing advance provision and information only. Contraception. 2006;74:1107.
  6. Raymond EG, Stewart F, Weaver M, et al. Impact of increased access to emergency contraceptive pills: a randomized controlled trial. Obstet Gynecol. 2006;108:10981106.
  7. Baecher L, Weaver MA, Raymond EG. Increased access to emergency contraception: why it may fail. Hum Reprod. 2009;24:8159.