 The present survey is based on a randomly selected sample with socio-demographic characteristics similar to the general population living in mainland France i.e. excluding Corsica, overseas departments, regions, and communities, and New Caledonia. A quota sampling method was used: sampling wastratified by residential area, size of the urban agglomeration, infant gender, mothers professional activity, occupational and socio-occupational status and adjusted for these different characteristics. This stratification was based on the population characteristics of the 2002 census of the National Institute for Statistics and Economic Research INSEE, Institut National de la Statistique et des Etudes Economiques. 