BACKGROUND: In low- and middle-income countries, pregnancy in adolescence represents an important public health issue. Rates of early pregnancy have significant social and economic consequences that extend beyond the individual sphere, impacting public/governmental budgets. AIM: To estimate the cost implications of early pregnancies from the perspective of the Brazilian Unified Public Health System. METHODS: This retrospective secondary data analysis focuses on assessing direct hospital costs. The study cohort comprises adolescents and young adults who underwent prenatal care at a reference maternity hospital between January and December 2021. Individual procedure costs were extracted from hospital records and converted into monetary values using the Brazilian Federal Fee. The sample size for each group was determined based on preliminary data collected during a pilot study. Descriptive analyses presented costs stratified by age groups. To estimate budgetary impacts and sensitivity we used national live birth incidence rates. RESULTS: The mean cost per case of adolescent pregnancy was US704.92 (SD: 1,707.74) and for adult pregnancy was US592.40 (SD: 941.43). The cost of hospital admission accounted for 61% of the total cost of adolescent pregnancies. The annual budget impact of pregnancies among women under 30 years was estimated at US1 billion, with 239 million coming from women under 20 years old. CONCLUSION: Pregnancy in adolescence may lead to a significant annual budget impact, representing 24% of costs attributed to pregnancies among women under 30 years. Costs related to hospital admissions and complications represent a substantial share of the total costs of adolescent pregnancy.