purpose: to investigate the interactions between maternal age and adverse perinatal outcomes in the state of rio grande do norte. methods: we analyzed official records of 57,088 infants in the state of rio grande do norte, from january 1997 to december 1997. data were obtained from the information system of the health ministry, brazil. the sample was divided into three groups i, ii and iii according to maternal age range: 10 to 19 years, 20 to 34, and 35 or more, respectively. the main outcome variables were: length of pregnancy, birth weight and mode of delivery. statistical analysis was performed using c2 test. results: preterm deliveries were 4.3% in the adolescent group vs 3.7% in group ii (p = 0.0028). the incidence of cesarean section was higher in group ii than in the other groups (p<0.001). low birth weight was significantly higher in groups i (8.4%) and iii (8.3%) when compared with group ii (6.5%) (p<0.0001). conclusions: we found a higher incidence of lower birth weight and preterm delivery in the adolescent group. in women 335 years old there was a high incidence of low birth weight and macrosomia. results suggest that cesarean sections are more common in women aged 20-34 years than in adolescent and older mothers.