OBJECTIVE: To study the relations between maternal occupational exposure to solvents during pregnancy and the risk of congenital malformations. METHODS: A prospective population-based cohort, specifically designed to study the impact of maternal exposure to solvents on the risk of congenital malformations, began in 2002 in three districts of Brittany (France). 3421 pregnant women were recruited until the end of 2005 by physicians before 19 weeks of gestation and followed through birth. Information on pregnancy outcomes was obtained from the hospital. Occupational exposure to solvents at the beginning of pregnancy was assessed from the women's self-reported occupational exposures at inclusion and from a job-exposure matrix (JEM). Sociodemographic characteristics, lifestyle factors, medical history, diseases during pregnancy were obtained at inclusion and from hospital records. Analyses were restricted to working women (n = 3005). Logistic regressions were used to adjust for potential confounders. RESULTS: 30.2% of the working women declared regular exposure to at least one product that may contain solvents. 21.3% of them were classified at least in the medium exposure category using the JEM. Occupations mainly classified as exposed by both assessment methods were hairdressers, nurses' aides, nurses and chemists/biologists. Significant associations were found between major congenital malformations and maternal occupational exposure to solvents, assessed by both self-report odds ratio (OR = 2.48, 95% CI 1.4 to 4.4 for regular exposure vs no exposure) and the JEM (OR = 3.48, 95% CI 1.4 to 8.4 for highest level of exposure vs no exposure). A significant dose-response trend was observed with both assessment methods. Several subgroups of major malformations were associated with maternal exposure to solvents (oral clefts, urinary malformations and male genital malformations). CONCLUSION: This study provides further evidence of an association between exposure to solvents during pregnancy and the risk of major malformations.