RESUMO
Objective: To compare the frequencies of newborn diseases in those newborns classified according to a weight/length rate and those classified by the adequacy weight for gestational age. Methods: A retrospective cross-sectional study by record assessment was carried out enclosing all the live newborns at Hospital Geral do Grajaú, from September to December, 2009 (n =577) classified according to the rate weight/length and also to the adequacy weight for gestational age. The 10 and 90 percentiles of the weight/length distribution, now designated as "indices" were calculated leading to the following classification: low index, for newborns below 54.8 g/cm; high index, for those over 75.8 g/cm; and average index, for the remaining newborns. According to the adequacy weight for gestational age the newborns were designated as pre-term for gestational age; term small for gestational age; appropriate term and large term. In this sample there were no small and large pre-term or post-term newborns. Major diseases were related to the index and adequacy extracts by the X2 test for a contingency table. Results: A significant association was found among low index, pre-term for gestational age newborns and term small for gestational age; between average index and appropriate for gestational age term newborns; and high index with large term appropriate for gestational age newborns (p< 0.001). Hypoglycemia (3.4%) was associated to both low and high indices, to appropriate for gestational age preterm newborns and to small for gestational age term newborns. Sepsis (3.1%) was associated to both low index and pre-term appropriate for gestational age newborns. The respiratory distress syndrome (1.3%) was associated to low index and pre-term appropriate for gestational age newborns. Other respiratory distress syndromes (3.8%) were associated to low and high indices but not to the adequacy for gestational age classification. Jaundice (14.9%) was not associated to the studied classifications. Perinatal asphyxia (12.6%) was associated to low index and pre-term newborns.