 During the first feed administration, the enrolled infants undergo a continuous monitoring of cerebral and splanchnic rSO2 by means of an INVOS 5100 oximeter. NIRS recording is performed from 30 minutes before to 3 hours after feeding administration. Cerebral and splanchnic rSO2 are recorded every 5 seconds. Baseline values are defined by the mean of the 15 minutes before the meal; values recorded after feeding administration are clustered into 5-minute intervals. 