Adolescent Pregnancy and Perinatal Outcomes: A Hospital‐Based Cross‐Sectional Study

ABSTRACT Background Adolescent pregnancy is linked to adverse perinatal outcomes, yet distinctions between early (10–14 years) and late (15–19 years) adolescence and the impact of prenatal care adequacy remain unclear. We compared perinatal outcomes across maternal‐age groups and explored the contribution of prenatal‐care inadequacy to the association between maternal age and preterm birth. Methods We conducted a hospital‐based cross‐sectional study using SINASC data from a tertiary referral centre in Brazil. Live births to mothers aged 10–24 years from 2015 to 2020 were classified as early adolescence (10–14 years), late adolescence (15–19 years), or 20–24 years (reference). Preterm birth (< 37 weeks), preterm‐birth severity, a birth‐weight‐percentile proxy, and prenatal‐care adequacy were assessed. Adjusted risk ratios (RRs) were estimated using modified Poisson regression with robust variance and multiple imputation (20 datasets). An exploratory g‐computation analysis evaluated the contribution of inadequate prenatal care (< 7 visits) to the maternal‐age–preterm‐birth association. Results Early and late adolescents had higher risks of preterm birth (RR 1.33 and 1.19) and inadequate prenatal care (RR 1.13 for both) compared to the reference group. Early adolescents also had increased risk of low birth‐weight percentile (RR 1.47). Inadequate prenatal care accounted for approximately 10% of the association between adolescent age and preterm birth. Conclusions Adolescent pregnancy, especially early adolescence, is associated with increased preterm birth and prenatal care inadequacy. While prenatal care partially explains this risk, substantial direct associations persist, highlighting the need for comprehensive interventions beyond prenatal visit frequency.