In very low birth weight (\<1500g) preterm infants, nutrition with mother's own milk, as opposed to formula, is associated with reduced morbidity and mortality. At present, the merits and risks of pasteurising mother's own milk (recommended if the mother is positive for cytomegalovirus) are unknown. This single-institution retrospective analysis aims at comparing mortality and morbidity of preterm infants below 1500g birth weight who were fed raw (unpasteurized) or pasteurized mother's own milk (in case the mother is positive for cytomegalovirus). The infant's sex into is taken into account as a possible confounder.