RESUMEN
STUDY OBJECTIVE: To compare the incidence of preterm birth and low birth weight infants in young and older primiparous adolescents versus young adults. DESIGN: Cross-sectional study. SETTING: Maternity hospital in Vitória, ES, Brazil. PARTICIPANTS: During a 5-year period, young primiparous women who delivered a singleton liveborn infant over 22 weeks were interviewed while in the postpartum ward. INTERVENTIONS: A single investigator performed all the individual interviews to collect sociodemographic variables and obtained gestational age and birth weight from the patients' charts before discharge. MAIN OUTCOME MEASURES: Participants were divided into 3 groups according to age: young adolescents (10-15 years), older adolescents (16-19 y) and young adults (20-24 y). The chi(2) test was used to compare the rate of preterm birth and low birth weight between the groups and analyze differences in sociodemographic characteristics between the 3 groups. P<0.05 was considered significant. RESULTS: A total of 1124 participants were included: 164 young adolescents, 537 older adolescents and 423 adults. The rate of preterm birth was similar in the 3 groups: 4.3%, 3.5% and 4.5%, for young adolescents, older adolescents and adults, respectively (P=0.48). The rate of low birth weight was significantly higher among young adolescents (9.7%) compared to older adolescents (6.1%) and young adults (3.5%) (P=0.012). CONCLUSIONS: The rate of preterm birth was similar in adolescents and young adults. Adolescent mothers under 16 years of age have a significantly higher incidence of low birth weight infants.