Objetivo: Materiales y métodos: Resultados: Conclusiones: Objective: To analyse perinatal outcomes in nulliparous adolescents compared with nulliparous women aged 20-29 years. Material and methods: This large hospital-based retrospective cohort study included singleton births at ≥. 24 weeks to women younger than 30 years from 2008 to 2009. The There were two cohorts: a) a study cohort consisting of nulliparous adolescents aged 11 to 19 years (n = 3555), and b) a control cohort comprising nulliparous women aged 20-29 years (n = 7040). In addition to a bivariate analysis, logistic regression was performed to adjust for confounding variables. Perinatal outcomes included low birth weight, preterm delivery, antepartum foetal death, caesarean section, and Apgar score at five minutes < 7. Results: Preterm delivery < 37 weeks was more frequent among adolescents than among women aged 20-29 years (7.5% vs 5.4% respectively, p<. 0.001). There was no difference in the number of neonates with low birthweight <. 2500. g (6.8% vs 5.8% in adolescents vs adults, respectively, p= 0.05), the rate of preterm delivery <. 34 weeks (1.7% vs 2.1% in adolescents vs adults, respectively, p= 0.17), or in preterm delivery < 28 weeks (0.4% vs 0.3% in adolescents vs. adults, respectively, p= 0.32). There were no differences in antepartum foetal deaths (0.7% vs 1.0% in adolescents vs adults, respectively, p= 0.11) or in Apgar score < 7 at 5 minutes (0.4% vs 0.4% in adolescents vs adults, respectively, p= 0.983). Logistic regression analysis showed a significant difference in the risk of preterm delivery < 37 weeks (OR = 1.3, 95% CI: 1.1-1.6), but not in low birthweight < 2500 g (OR = 1.0, 95% CI 0.8-1.3). Conclusions: Preterm delivery < 37 weeks was more frequent in nulliparous adolescents than in women aged 20-29 years. There was no association between pregnancy in nulliparous adolescents and other adverse perinatal outcomes such as low birth weight, low Apgar score and antepartum foetal death.