Contraceptive failure in the first two years of use: differences across socioeconomic subgroups.

CONTEXT While differences in levels of contraceptive use across socioeconomic subgroups of women have narrowed greatly over time, large disparities remain in rates of unintended pregnancy. One reason is variations in the effectiveness with which women and their partners use contraceptive methods. METHODS Data on contraceptive use and accidental pregnancy from the 1988 and 1995 National Surveys of Family Growth were corrected for abortion underreporting and pooled for analysis. Use-failure rates were estimated for reversible methods during the first year, second year and first two years of use, for subgroups of women of various characteristics. RESULTS The average failure rate for all reversible methods, adjusted for abortion underreporting, declines from 13% to 8% from the first year of method use to the second year. First-year failure rates are highest among women using spermicides, withdrawal and periodic abstinence (on average, 23-28% in the first year), and lowest for women relying on long-acting methods and oral contraceptives (4-8%). On average, they exceed 10% for all users except women aged 30-44, married women and women in the highest poverty-status category. The chance of accidental pregnancy does not differ significantly between method users younger than 18 and those aged 18-19. CONCLUSION Both user and method characteristics determine whether contraceptive users will be able to avoid unintended pregnancy. Family planning providers should help clients to identify methods that they are most likely to use successfully, and counsel them on how to be consistent users and to avoid behaviors that contribute to method failure.