births and the rate was about two times higher among
adolescents < 18 years than among mothers of the
other age groups, and was approximately 30% higher
among adolescents aged 18 and 19 years. Preterm
births were also more frequent among adolescents than
among mothers aged 20 to 34 years. Adolescents more
frequently received care during delivery at the Brazilian
Unifi ed Health System (SUS) and had lower rates of
cesarean delivery, i.e., about half the rate observed for
the remaining women (Table 2).
Unadjusted analysis (Table 3) showed that maternal
age, adequacy of prenatal care, family income, marital
status, maternal schooling, smoking during pregnancy,
alcohol intake during pregnancy, prenatal category and
preterm birth were statistically signifi cant factors for
infant LBW (p < 0.05).
Persisting risk factors for LBW after adjusting for
confounding factors (Table 4) were: mothers who did
not receive prenatal care (OR 2.35; 95%CI 1.10;5.05)
and smoking during pregnancy (OR 2.04; 95%CI
1.28;3.25). Each week of increased gestational age
represented a 47% reduction of the risk of LBW
(OR 0.53; 95%CI 0.49;0.56). There was interaction
between maternal age and marital status, with the