Peer-reviewed article

Return-on-investment for interventions to reduce adolescent pregnancy and child marriage in Southeast Asia: a five-country modelling study

W.P.T.M. Wickramaarachchi, Christine Marie Habito, Davide De Beni, Federica Maurizio, Sylvia Wong et al. · 1 Jul 2026

Abstract

INTRODUCTION: Adolescent pregnancy remains a concern in Southeast Asia, with pregnancy both a driver and an outcome of child marriage or union. For Cambodia, Indonesia, the Philippines, Lao People's Democratic Republic (PDR) and Malaysia, this study aimed to calculate the benefit-cost ratio of investing in evidence-based interventions to prevent adolescent pregnancy and child marriage, considering their complex interdependencies. METHODS: The population of girls aged 15-19 years was modelled at a national level, stratified by marriage, poverty and school enrolment status (known risk factors for pregnancy). Time-varying inputs for sociodemographics, contraception use, pregnancy and marriage were taken from population surveys (eg, Demographic and Health Survey [DHS]) and census data. A targeted review identified interventions with sufficient cost and effectiveness evidence for inclusion in modelling. A baseline scenario (constant intervention coverage over 2024-2030) was compared with investment scenarios, with interventions scaled up to reach an aspirational 95% coverage by 2030. RESULTS: Evidence-based interventions included in-school comprehensive sexuality education, cash transfers, educational support, life skills training, livelihood training and community dialogue. Across the five countries, baseline scenario intervention costs were US$1.4 billion over 2024-2030, with a projected 2.4 million unintended adolescent pregnancies and 2.1 million child marriages among girls 15-19 years. Scale-up of all interventions to reach 95% coverage by 2030 would cost an additional US$5.0 billion and, in return, avert 1.3 million unintended pregnancies and 1.1 million child marriages. This was estimated to generate US$13.2 billion in economic benefits by 2050 with a benefit-cost ratio of 2.7, increasing to 9.7 if interventions were maintained to 2050 and lifetime benefits considered. Achieving a more modest 50% intervention coverage by 2030 produced similar benefit-cost ratios but with reduced total impact. CONCLUSION: For every US$1 invested to scale up and maintain high coverage of evidence-based interventions to reduce child marriages and adolescent pregnancies in Cambodia, Indonesia, the Philippines, Lao PDR and Malaysia, US$9.7 could be returned to the economy in the longer term.