The levels of bisphenol A (BPA) and phthalate exposure among the French population are unknown. However, given the widespread use of these substances and current regulations, it would be valuable to have such data based on a sample representative of the entire population. One of the objectives of the ELFE cohort (French Longitudinal Study from Childhood) is to analyze these exposures and assess their impact on the health of a subsample of 20,000 children born in 2011 and followed through adulthood. The national study was launched in March 2011. It involves collecting biological samples taken in maternity wards to assess the exposure levels of pregnant women and their babies. This phase was tested in a pilot study conducted by the French Institute for Public Health Surveillance (InVS) and the National Institute for Demographic Studies. (R.A.)