U.S. women's one-year contraceptive use patterns, 2004.

CONTEXT Unintended pregnancies occur far too often in the United States, and half occur when couples fail to practice contraception. Improved measures of the continuity of women's contraceptive use, nonuse and switching patterns can help identify ways to reduce unintended pregnancy. METHODS A nationally representative sample of 1,978 adult women at risk of unintended pregnancy was surveyed by telephone in 2004. Respondents provided detailed information about contraceptive use and periods of stopping or switching methods during the past year. A typology of patterns of contraceptive use was created, classifying women into mutually exclusive categories according to their exposure to pregnancy risk. RESULTS Twenty-three percent of women at risk of unintended pregnancy were exposed to a high risk of pregnancy because of gaps in contraceptive method use in the year prior to the survey--8% were consistent nonusers, and 15% experienced 1-11 months of nonuse while at risk. More than half of women used a method during each of the previous 12 months-38% used the same method or methods all year, and 24% switched methods. Fifteen percent of women had gaps in contraceptive use when they were not at risk. Women reported a variety of reasons for their gaps in contraceptive use, including method-related difficulties and side effects, infrequent sex and being ambivalent about avoiding pregnancy. CONCLUSIONS Strategies for reducing gaps in contraceptive use include improved counseling to help women both choose the right method and continue method use, especially when they have periods of infrequent sexual activity or are experiencing method-related side effects or problems.