Infants will be randomized while they are hospitalized in the NICU of Clinica Alemana de Santiago or in the NICU of Hospital San Jose. At the time of randomization, it will be defined whether the infant should attend medical check-ups at 2, 6 and 12 months of corrected gestational age with a neonatologists trained in Alarm Distress Baby Scale, or with a physician not trained, who will not perform the treatment.