 Hypoglycemia is frequent in very low birth weight VLBW neonates and compromises their neurological outcome. The aim of this study was to compare real-time continuous glucose monitoring system RT-CGMS to standard method by intermittent capillary blood glucose testing in detecting and managing hypoglycemia. The investigators calculated a number of 48 neonates to be randomized between 2 ways of glucose level monitoring for their 3 first days of life : either by RT-CGMS CGM-group, or by intermittent capillary glucose testing IGM-group associated with a blind-CGMS to detect retrospectively missed hypoglycemia. The investigators hypothesis is that in the CGM group number and duration of hypoglycemia will be lower. 