Data from the Brazilian Ministry of Health and the literature indicate that adolescents may be overrepresented in the prevalence of maternal morbidity and mortality and neonatal complications. This study focused on childbirth and live newborns among adolescent and young adult mothers in the municipality of Feira de Santana, Bahia, identifying risk factors for morbidity and mortality. A cross-sectional cohort study was conducted based on data from the Information System on Live Births (SINASC) in the municipality in 1998, totaling 5,279 live births among adolescent (10 to 19 years) and young adult mothers (20 to 24 years). Variables were age, schooling, prenatal care, gestational care, form of delivery, and birthweight. The authors measured the association between maternal age and the child's birthweight, while controlling potential confounders. Some 21.6% of live births were to adolescent mothers, 51.2% of whom had not finished primary school; there was an association between the 10 to 16-year age bracket and incomplete primary schooling, lack of prenatal care, and low and insufficient birthweight as compared to the other age brackets; there was also a high rate of underrecording in the SINASC. The results suggest the need for specific measures focusing on the reproductive health of adolescents in the municipality.