In our service, all preterm infants start to be fed milk expressed from their own mother unprocessed or pasteurized breast milk from the milk bank. When a volume of 100 mL·kg-1·day-1 is reached, the milk is enriched with a fortifying agent. When the patient is clinically stable and receiving a full diet (140–160 mL·kg-1·day-1), and if the maintenance of maternal lactation is not possible, a full or partial transition to infant milk formulas is started.