BACKGROUND: Despite the widespread use of highly effective contraceptive methods in France, one in every three pregnancies is unintended, of which 65% occur while using contraceptives. In the USA, 49% of pregnancies are unintended, half of which result from contraceptive failure. This study provides estimates of method-specific failure rates among French women. METHODS: We use data from the 2000 Cocon Study, a population-based cohort, comprising a representative sample of 1689 women aged 18-44 years who described their contraceptive history. Piecewise-constant hazards models were used to estimate method-specific contraceptive failure rates during the first 5 years of contraceptive use. A random effect was introduced to take into account the fact that some women contribute more than 1 contraceptive episode. These same models were used to assess the effects of socio-demographic characteristics on the probability of contraceptive failure among pill, intrauterine device (IUD) and condom users. RESULTS: Overall, 2.9% of women experienced a contraceptive failure in the first year of use and 8.4% in the first 5 years of use. The IUD had the lowest first year failure rate (1.1%), followed by the pill (2.4%), the condom (3.6%), fertility awareness methods (periodic abstinence or safe period by temperature) (7.7%), withdrawal (10.1%) and spermicides (21.7%). These failure rates varied little by user characteristics. CONCLUSIONS: Lower failure rates among French women compared with those reported for US women suggest differences in contraceptive practices which need to be further explored.
BACKGROUND: Despite the widespread use of highly effective contraceptive methods in France, one in every three pregnancies is unintended, of which 65% occur while using contraceptives. In the USA, 49% of pregnancies are unintended, half of which result from contraceptive failure. This study provides estimates of method-specific failure rates among French women. METHODS: We use data from the 2000 Cocon Study, a population-based cohort, comprising a representative sample of 1689 women aged 18-44 years who described their contraceptive history. Piecewise-constant hazards models were used to estimate method-specific contraceptive failure rates during the first 5 years of contraceptive use. A random effect was introduced to take into account the fact that some women contribute more than 1 contraceptive episode. These same models were used to assess the effects of socio-demographic characteristics on the probability of contraceptive failure among pill, intrauterine device (IUD) and condom users. RESULTS: Overall, 2.9% of women experienced a contraceptive failure in the first year of use and 8.4% in the first 5 years of use. The IUD had the lowest first year failure rate (1.1%), followed by the pill (2.4%), the condom (3.6%), fertility awareness methods (periodic abstinence or safe period by temperature) (7.7%), withdrawal (10.1%) and spermicides (21.7%). These failure rates varied little by user characteristics. CONCLUSIONS: Lower failure rates among French women compared with those reported for US women suggest differences in contraceptive practices which need to be further explored.