In Brazil, neonatal mortality is the most common cause of infant mortality. The majority of deaths occur in very low birthweight newborns. This longitudinal study assesses factors associated with mortality risk in very low birthweight newborns during the first 27 days of life. Relative risk of mortality was assessed for each variable, and the most statistically significant variables were selected for the multivariate model, in which odds ratios were calculated using logistic regression. Factors associated with decreased mortality risk were: prenatal corticosteroid (OR = 0.40; 90%CI: 0.23-0.74) and total parenteral nutrition (OR = 0.06; 90%CI: 0.02-0.15). Factors associated with increased mortality risk were: male gender (OR = 2.19; 90%CI: 1.27-4.00); maternal hemorrhage (OR = 4.28; 90%CI: 1.27-14.46); use of mechanical ventilation (OR = 18.83; 90%CI: 5.15-68.87); CRIB (OR = 4.48; 90%CI: 2.43-8.27); and birthweight. Selective use of prenatal corticosteroid should be encouraged in order to reduce neonatal mortality and morbidity.