As part of the implementation of a system to monitor children’s diet and nutritional status during their first year of life (Épifane), the Unit for Nutritional Surveillance and Epidemiology (Usen)—a joint unit of the French Institute for Public Health Surveillance and Paris 13 University—conducted a pilot study in 2010. This pilot study was conducted among a sample of 190 mothers and their newborns, recruited from 10 maternity wards in mainland France. The objectives of the pilot study were to assess the acceptability and feasibility of the national study and to choose between two data collection methods for longitudinal follow-up at 1 month, 4 months, 8 months, and 12 months of age. The acceptance rate among mothers in the maternity wards was 81%. The attrition rate (loss to follow-up and refusals during the longitudinal follow-up) was 15% at the end of the follow-up, which was limited to 8 months for the pilot study. The pilot study thus concluded that the study was feasible and acceptable to mothers. For the longitudinal follow-up, the pilot study led to the decision to use a mixed data collection method via telephone and questionnaire (online or possibly paper-based) rather than data collection exclusively by telephone. It also provided numerous methodological insights that were taken into account in preparing the national study. These lessons primarily concerned the methods for contacting maternity wards, sample selection, the method for including mothers, the content of the questionnaires, and monitoring the provider’s work. This report presents a summary of these various elements. (R.A.)