Contraceptive Failure Rates in France: Results From a Population-based Survey

C. Moreau; J. Trussell; G. Rodriguez; N. Bajos; J. Bouyer

Disclosures

Hum Reprod. 2007;22(9):2422-2427. 

In This Article

Abstract and Introduction

Abstract

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.

Introduction

Despite the widespread use of highly effective contraceptive methods it is estimated that 49% of pregnancies are unintended in the USA: there were 3.1 million in 2001 alone, the last year for which data are available (Finer and Henshaw, 2001). Half (48%) of these pregnancies were due to contraceptive failure, while the other half occurred to the small minority (11%) of women not using any method of contraception (Finer and Henshaw, 2001; Mosher et al., 2004). A similar pattern is observed in France despite a high prevalence of use of highly effective reversible methods of contraception [in 2000, 82% of contraceptive users were using the pill or the intrauterine device (IUD) (Bajos et al., 2003)]. A recent population-based survey in France found that one in three pregnancies was reported as unintended, of which 65% occurred among women who were using contraceptives at the time they got pregnant (Bajos et al., 2003). These results reflect the difficulties women experience when using contraceptive methods that require adherence such as taking a pill each day or using a condom at each act of intercourse.

Most available information on contraceptive failure comes from clinical trials. Clinical trials have the advantage of collecting prospective data from women who are closely monitored, and failure rates during perfect (correct and consistent) contraceptive use can be estimated; however, such trials almost surely do not reflect conditions under which contraceptive methods are actually used (or misused) in the general population. The second source of information is provided by population-based surveys that are more likely to reflect the typical conditions of use of contraceptives but may fail to provide as accurate information on use as do clinical trials. A few studies, mostly conducted in the USA using data from the National Survey of Family Growth (NSFG), have been performed using this later approach (Trussell et al., 1990; Trussell and Vaughan, 1999). Contraceptive failure rates during typical use vary by user characteristics (age, parity and social background) (Schirm et al., 1982; Ranjit et al., 2001); this finding suggests that contraceptive failure rates may also vary by country with different contraceptive practices. In advanced industrial societies, only one Australian study, using data from the national Australian Fertility Survey, has produced contraceptive failure rates estimates based on a similar methodology (Bracher and Santow, 1992). However, that study focused only on contraceptive failure rates during the first use of the method.

This study provides estimates of method-specific failure rates among women in France. In addition to differences by method used and by duration of use, the analysis explores the differences in failure rates by women's social and demographic background characteristics.

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