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Contraceptive Failure Rates - Pregnancy and Disease Prevention

The prevailing perception regarding contraception is that it offers almost perfect protection against pregnancy and disease, yet in reality this isn't the case.

Pregnancy

Some 9-12 percent of women become pregnant within the first year of contraceptive use ^[1].  However, this range does not reflect the specific failure rates associated with the each method.

Consider the male condom - for women who rely on it for their primary protection against pregnancy, with typical use almost 15 of them will get pregnant within a year.  Table 1 shows contraceptive failure rates adjusted for abortion underreporting.

Table 1.  Corrected and standardized method failure rates, by method and duration.

(Source:  Family Planning Perspectives, Table 1, p 60, Vol 31, Number 2, March / April 1999)

Of significant importance is the increase in failure rates over time, even amongst the methods with lower failure rates. 

Disease

Only one contraceptive method offers any level of protection against sexually transmitted diseases - the condom.

As with preventing pregnancy, condoms are not perfect in preventing disease transmission.  The failure rate in preventing HIV transmission is subject to debate, but typical effectiveness of condoms in preventing HIV transmission rages from 80%^[3] to 95%.^[4][2]   But this also means that they have an ineffective rate of 5% to 20%. 

Condoms are not 100% effective in preventing transmission of other "discharge diseases" as well, including gonorrhea, Chlamydia, and trichomoniasis. 

Condoms are less effective in preventing the transmission of genital ulcer diseases (genital herpes, syphilis, and cancroids) or HPV due to the fact they can transmitted via areas not covered by the condom. ^[5] 

A problem on the horizon related to the less than perfect effective rate of condoms in disease prevention are drug resistant strains of sexually transmitted diseases.  In recent years, strains of multi drug resistant gonorrhea and syphilis have developed, posing a significant public health threat.

Of significant interest is the warning given by the CDC on the issue of disease prevention:

The surest way to avoid transmission of sexually transmitted diseases is to abstain from sexual intercourse, or to be in a long-term mutually monogamous relationship with a partner who has been tested and you know is uninfected ^[5]

Other methods (aside from male/female condoms) do not offer protection against disease, and in fact, some methods contribute to disease.  Hormonal based contraceptives are associated with breast, liver, and cervical cancers as well as blood clots and strokes.  (However, oral contraceptives have been associated with a decrease in endometrial cancer.)

Conclusion

Contraceptives are not as effective in pregnancy or disease prevention as is commonly believed. 

For Further Reading

Condom Expose (HLI)

Male Latex Condoms and Sexually Transmitted Diseases (CDC)

Endnotes

[1]  About one in 10 Women using Contraceptives Experience an Accidental Pregnancy, The Alan Guttmacher Institute, available at http://www.guttmacher.org/media/nr/newsrelease3102.html

[2]  The Effectiveness of Condoms in Reducing Heterosexual Transmission of HIV,  Family Planning Perspectives Volume 31, Number 6, November/December 1999 , The Allan Guttmacher Institute, available at http://www.guttmacher.org/pubs/journals/3127299.html

[3] USAID: HIV/STI Prevention and Condoms, USAID, available at http://www.usaid.gov/our_work/global_health/aids/TechAreas/prevention/condomfactsheet.html

[4] Pinkerton SD, Abramson PR, Effectiveness of condoms in preventing HIV transmission , social science An Medicine 44/9, pp1303-1312, May 1997, available at http://www.salud.gob.mx/conasida/preven/condon/pinker01.htm

[5] Fact Sheet for Public Health Personnel: Male Latex Condoms and Sexually Transmitted Diseases, Centers for Disease Control and Prevention (CDC), available at http://www.cdc.gov/nchstp/od/condoms.pdf