Objectives: This study aims to identify birth weight variation according to maternal characteristics and gestational weight gain. Methods: It is a cross-sectional descriptive study with 433 puerperal women (≥ 20 years old) who attended a public maternity hospital in Rio de Janeiro. The data were collected through interviews with the women and access to their medical records. Several models were tested using linear regression, using the stepwise method to identify the predictive variables of birth weight. Results: The mean maternal age and gestational age at the end of pregnancy were 27 years old (± 5.09 years) and 39 weeks (+ 1.68 weeks), respectively. The data shows that the mean number of prenatal and nutritional prenatal care appointments were 8.24 (± 2.98) and 2.26 (± 2.33), respectively. Among the predictor variables of birth weight, total gestational weight gain (ß = 25.29; p = 0.000), pre-gestational BMI (ß =13.02; p = 0.037), and the number of pre-natal care appointments (ß = 28.21; p = 0.007) were highlighted. The association of weight gain in the three trimesters was also verified. Conclusions: This study confirms the interface between adequacy of the pre-gestational and gestational nutritional status and some maternal characteristics with birth weight. Nutritional care should be recognised aspart of the actions during pre-natal assistance.