 Early identification of preterm infants at high risk of gastrointestinal complications could help clinical decisions on the introduction and the advancement of enteral feeding. The administration of the first feed in healthy preterm infants leads to a post-prandial increase of superior mesenteric artery SMA blood flow, detected by Doppler ultrasound. A significant correlation between early feeding tolerance and increased SMA blood flow velocity has been further observed one hour after the first feed. 