Results-In 2002, 12.4% of all episodes of contraceptive use ended with a failure within 12 months after initiation of use. Injectable and oral contraceptives remain the most effective reversible methods used by women in the U.S., with probabilities of failure during the first 12 months of use of 7% and 9%, respectively. The probabilities of failure for withdrawal (18%) and the condom (17%) are similar. Reliance on fertility-awareness-based methods results in the highest probability of failure (25%). Population subgroups experience different probabilities of failure, but the characteristics of users that may predict elevated risks are not the same for all methods.Conclusion-There was no clear improvement in contraceptive effectiveness between 1995 and 2002. Failure rates remain high for users of the condom, withdrawal and fertility-awareness methods, but for all methods, the risk of failure is greatly affected by socioeconomic characteristics of the users.

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Measures of wantedness based on women's feelings about their pregnancy may correlate more closely with important pregnancy outcomes than do traditional measures of intendedness.

CONTEXTContraceptive failure rates measure a woman's probability of becoming pregnant while using a contraceptive. Information about these rates enables couples to make informed contraceptive choices. Failure rates were last estimated for 2002, and social and economic changes that have occurred since then necessitate a reestimation.METHODSTo estimate failure rates for the most commonly used reversible methods in the United States, data from the 2006–2010 National Survey of Family Growth were used; some 15,728 contraceptive use intervals, contributed by 6,683 women, were analyzed. Data from the Guttmacher Institute's 2008 Abortion Patient Survey were used to adjust for abortion underreporting. Kaplan‐Meier methods were used to estimate the associated single‐decrement probability of failure by duration of use. Failure rates were compared with those from 1995 and 2002.RESULTSLong‐acting reversible contraceptives (the IUD and the implant) had the lowest failure rates of all methods (1%), while condoms and withdrawal carried the highest probabilities of failure (13% and 20%, respectively). However, the failure rate for the condom had declined significantly since 1995 (from 18%), as had the failure rate for all hormonal methods combined (from 8% to 6%). The failure rate for all reversible methods combined declined from 12% in 2002 to 10% in 2006–2010.CONCLUSIONSThese broad‐based declines in failure rates reverse a long‐term pattern of minimal change. Future research should explore what lies behind these trends, as well as possibilities for further improvements.

The risks of pregnancy during typical use of reversible methods of contraception are considerably higher than risks of failure during clinical trials, reflecting imperfect use of these methods rather than lack of inherent efficacy. High rates of method-related discontinuation probably reflect dissatisfaction with available methods.