Findings from a systematic review, conducted by Dr Lindsay Mangham-Jefferies and colleagues for the IDEAS project at the London School of Hygiene & Tropical Medicine. Funded by the Bill & Melinda Gates Foundation. Key messages: •Cost-effective strategies are needed to improve the use and provision of maternal and newborn health care, and increase the coverage of maternal and newborn health interventions. •Demand and supply-side strategies can be cost-effective, and there is strong evidence in certain contexts. •Questions remain about the extent to which both costs and effects vary by implementation, context and scale. •Evidence is limited by the number of studies on different types of demand and supply strategies and the lack of high quality studies using comparable cost-effectiveness measures. •More attention should be given to the design and reporting of cost-effectiveness studies.