Biparietal diameter, occipitofrontal diameter, cephalic index and occipitofrontal circumference were measured in 108 newborns delivered at term by cesarean section. Statistical analyses were carried out to assess the relationship between each of the parameters and birth weight. Particular attention was paid to the cephalix index/birth weight, the former being assumed as an expression of head shape. No correlation between birth weight and cephalic index was observed. Birth weight best correlates with occipitofrontal circumference.