This thesis uses a complexity thinking approach to investigate the implementation of development strategies to improve maternal health taking the province of East New Britain, in Papua New Guinea, as a case study. A key global strategy for improving maternal and neonatal health is that every woman and baby receives assistance from an appropriately qualified and skilled health worker with midwifery skills. However, globally there continues to be a lack of universal care, with one in four births occurring in the absence of skilled assistance. In Papua New Guinea, access to skilled care remains inequitable and, since independence, there has been little reduction in the numbers of women and babies experiencing poor outcomes. Using a qualitative inquiry approach, the thesis employs a range of methods including analysis of historical and contemporary documents, interviews, and observation of clinical and administrative practice, to better understand the maternal health care system. Selected conceptual tools from complexity thinking guide analysis, namely path dependence and system lock-ins; connectivity and nonlinearity; and self-organisation and emergence. This work contributes to building knowledge of implementation of development strategies by highlighting the multiple ways that the maternal health care system intersects with other systems. It argues that these systems are all dynamic constructs shaped by historical, social and political conditions. As such, midwifery and health management practice are constrained by system constructs which do not recognise the importance of the role of midwives in protecting maternal and neonatal health. Constraints include inadequate prioritisation of maternal health to ensure midwives are enabled to provide care across their full scope of practice; non-establishment of maternal health review committees; and little agreement regarding education for cadres of health workers expected to provide women and neonates with midwifery care during pregnancy, labour and birth, and postpartum. In order to ensure all women receive skilled midwifery care, and thus improve maternal and neonatal health, this thesis argues it is crucial for development strategies to remain cognisant of, and engage with, the broader health system and other intersecting social systems. In addition to building technical midwifery capacity, development strategies must constructively disrupt the status quo to generate sufficient endogenous system change to enable the prioritisation of maternal health. This requires a balance between international recommendations, and existing systems realities and endogenous, context-dependent solutions.