Background: Understanding the cost-effectiveness and affordabilityof interventions to reduce maternal and newborn deaths is criticalto persuading policymakers and donors to implement at scale. Theeffectiveness of community mobilisation through women’s groups andhealth facility quality improvement, both aiming to reduce maternaland neonatal mortality, was assessed by a cluster randomised controlledtrial conducted in rural Malawi in 2008-2010. In this paper, we calculateintervention cost-effectiveness and model the affordability of theinterventions at scale. Methods: Bayesian methods are used to estimatethe incremental cost-effectiveness of the community and facilityinterventions on their own (CI, FI), and together (FICI), comparedto current practice in rural Malawi. Effects are estimated with MonteCarlo simulation using the combined full probability distributionsof intervention effects on stillbirths, neonatal deaths and maternaldeaths. Cost data was collected prospectively from a provider perspectiveusing an ingredients approach and disaggregated at the intervention(not cluster or individual) level. Expected Incremental Benefit,Cost-effectiveness Acceptability Curves and Expected Value of Information(EVI) were calculated using a threshold of USD780 per disability-adjustedlife-year (DALY) averted, the per capita gross domestic product ofMalawi in 2013 international USD. Results: The incremental cost-effectivenessof CI, FI, and combined FICI was USD79, USD281, and USD146 per DALYaverted respectively, compared to current practice. FI is dominatedby CI and FICI. Taking into account uncertainty, both CI and combinedFICI are highly likely to be cost effective (probability 98 percent and93 percent, EVI USD210,423 and USD598,177 respectively). Combined FICI isincrementally cost effective compared to either intervention individually(probability 60 percent, ICER USD292, EIB USD9,334,580 compared to CI). Futurescenarios also found FICI to be the optimal decision. Scaling-upto the whole of Malawi, CI is of greatest value for money, potentiallyaverting 13.0 percent of remaining annual DALYs from stillbirths, neonataland maternal deaths for the equivalent of 6.8 percent of current annualexpenditure on maternal and neonatal health in Malawi. Conclusions:Community mobilisation through women’s groups is a highly cost-effectiveand affordable strategy to reduce maternal and neonatal mortalityin Malawi. Combining community mobilisation with health facilityquality improvement is more effective, more costly, but also highlycost-effective and potentially affordable in this context.