Successful postnatal pulmonary adaptation is dependent on cessation of fetal fluid secretion into the luminal space of the lung and a switch to fluid absorption during the perinatal period. Most infants undergo this transformation rapidly, but some encounter difficulties.Failure in adaptation may result, in preterm infants, in respiratory distress syndrome (RDS) and, in near-term and term infants, in transient tachypnea of the newborn (TTN). In both entities, among other causes, lung liquid clearance, i.e. the inability to clear the lung of perinatal fluid, may be ineffective.1-4 In addition, there are data connecting bronchopulmonary dysplasia (BPD) to decreased ion transport.5-7 However, only limited data are available on the association of lung fluid transport and neonatal respiratory distress in human infants.