Urinary samples will be collected onto a gauze compress, during the first 24 hours of life, at day three, and at 1, 3, 6 and 12 months. A blood sample will be obtained from systematic umbilical cord blood collection at birth and during the Guthrie test at day three. Aldosterone and renin concentrations will be measured in BICETRE Hospital laboratory. Plasma and urinary electrolyte concentrations will be measured in the Biochemistry department. DNA samples will also be gathered from umbilical cord blood for future genetic investigations (functional polymorphisms of the MR gene).