To analyze the association of natal factors with the severity of neonatal brain white matter lesion (WML) by controlling the birth weight, we identified newborns with WML who were divided into: those with WML evolution towards resolution of the ultrasound image (less severe), and those who evolved with cist formation and/or ventriculomegalia and/or hemorrhage (greater severity). There were differences among the twelve variables (hyponatremia, anemia, infection, retinopathy, broncopulmonary dysplasia, hypoalbuminemia, persistence of the arterial canal, altered audiometry, early respiratory distress, birth weigh below 2,500 g, weight per category, and prematurity) between the two groups (p<0.05), being that nine variables (hyponatremia, infection, retinopathy, hypoalbuminemia, persistence of the arterial canal, early respiratory distress, low weight, prematurity, and weight per category) remained statistically different (p<0.01) after the logistic regression analysis. When the variables were analyzed by birth weight category none of them presented statistical significance. This study suggests that birth weight is the major factor--likely the only one--associated to the severity of neonatal brain white matter lesion.