Growth restriction in preterm infants has been related to a poor neurodevelopment outcome. To define the incidence of postnatal growth restriction in premature babies ≤1,500 grams and to detect related clinical or biochemical markers. Retrospective longitudinal observational study. Multivariate linear regression models were used to determine variables that can predict the change in weight z-score during admission. The study included 130 patients with a mean birthweight of 1,161±251grams and a gestational age of 29.9±2.5 weeks. At hospital discharge, 59.2% had a weight below P10.During admission, the z-scores of weight and length decreased by -0.85±0.79 and -1.09±0.65, respectively.The largest decrease in z-score occurred during NICU admission, with a weight gain rate of 6.6±8.8g/Kg/day, after which growth acceleration took place (16.7±3.8g/Kg/day), but was insufficient to catch-up.Higher levels of urea were negatively correlated with the change in the z-score of weight (P<.001), and a weight