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  • Fast Facts

    Dr Margaret answers emailers’ embarrassing problems
    in this monthly problem page.

    Effectiveness of condoms

    Dear Dr Margaret
    How good are condoms at preventing pregnancy?

    You are not the only person who is confused about how effective condoms actually are for preventing pregnancy (contraception). May be you saw the episode of Friends in which Rachel tells Ross that she is pregnant. Ross was astonished because they had used a condom and had had sex only once. Then he read from the condom package that ‘condoms are only 97% effective’. In the USA alone, 1.67 million teenagers saw this episode. A survey afterwards showed that many of these viewers were worried by it, and it made them think that condoms were not as reliable as they had previously thought.

    No contraceptive is 100% effective (although the Mirena intrauterine system for women comes close). For example, research shows that half of all pregnancies in the USA are unintended and, of these, half occur to women who say they were practising contraception in the month they conceived.

    However, latex condoms (the most common type) can be a good contraceptive. If used absolutely correctly, the failure rate is about 3% per year. This means that if 100 couples have regular sex for a year, using condoms correctly every time, 3 of the women will become pregnant. This is the same as the ‘97% effective’ statement that Ross read on the package.

    But for condoms to be 97% effective, they do have to be used absolutely correctly. This means not damaging it while removing the foil wrapper, not damaging it while putting it on, putting it on the right way round, unrolling it to its full length, putting it on before the penis touches the woman’s genitals and holding it on after ejaculation. Have a look at our Condoms: Dos and Don’ts section for more information.

    In real life, many people do not use condoms as carefully as they should. This means that the real-life failure rate is, on average, about 9–14% (depending on which research you believe). So it really is important to use condoms properly – their effectiveness depends to a large extent on you.

    Condoms also provide good protection against sexually transmitted infections, such as chlamydia, gonorrhoea and HIV, but only if they are used correctly.

    Sources of information
    Black K, Kubba A. What’s new in contraception? Trends in Urology, Gynaecology and Sexual Health 2004;Jan/Feb:22–25.

    Collins RL et al. Entertainment television as a healthy sex educator: the impact of condom-efficacy information in an episode of Friends. Pediatrics 2003;112(5):1115–21.

    Gallo MF et al. Non-latex versus latex male condoms for contraception. Cochrane Database Systematic Reviews 2003(2):CD003550.

    Trussell J, Vaughan B. Contraceptive failure, method-related discontinuation and resumption of use: results from the 1995 National Survey of Family Growth. Family Planning Perspectives 1999;31:64–72.


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