<![CDATA[Background: Child marriage and adolescent pregnancy pose risks to the reproductive health of young women and their infants. Comprehensive provincial data on child marriage are not publicly available; therefore, this article examines national trends and available provincial evidence. Objectives: To describe trends in adolescent birth rates and child marriage in Indonesia, compare them with four other Southeast Asian countries, and assess the association between the two. Methods: A time-series ecological study using secondary data. Adolescent birth rates (births per 1,000 females aged 15–19 years) from 1990 to 2023 were obtained from the World Bank’s World Development Indicators for Indonesia, the Philippines, Thailand, Vietnam, and Malaysia. The percentage of women aged 20–24 who were married before age 18 (2008–2024) was obtained from reports by the Central Statistics Agency (BPS) and UNICEF, as well as publications derived from BPS data. Annual rates of change were calculated using log-linear regression across three periods; trends in child marriage were analyzed using linear regression; and the relationship between the two was assessed using Spearman’s and Pearson’s correlations. Results: Indonesia’s adolescent birth rate declined from 74.8 to 26.4 per 1,000 (−64.7%) between 1990 and 2023. The annual rate of decline was −2.96% from 1990 to 2004, slowed to −1.07% from 2005 to 2012, and increased to −5.08% from 2013 to 2023. Child marriage declined from 14.67% (2008) to 5.9% (2024), with a decrease of approximately 0.71 percentage points per year from 2016 to 2024 (R² = 0.89). The two time series were correlated from 2016 to 2023 (ρ = 0.93; 95% CI 0.53–0.99; n = 8), but both declined over time, so the correlation does not indicate causation. In 2018, the percentage of child marriages in provinces with available data ranged from 4.68% (Riau Islands) to 19.43% (West Sulawesi). Conclusion: Significant progress has been made, but the rate of decline has slowed, and disparities among provinces remain substantial. Analysis of adolescent pregnancies by province requires the publication of complete provincial data.]]>
