In high-income countries, medical interventions to address the known risks associated with pregnancy and birth have been largely successful and have resulted in very low levels of maternal and neonatal mortality. In this Series paper, we present the main care delivery models, with case studies of the USA and Sweden, and examine the main drivers of these models. Although nearly all births are attended by a skilled birth attendant and are in an institution, practice, cadre, facility size, and place of birth vary widely; for example, births occur in homes, birth centres, midwifery-led birthing units in hospitals, and in high intervention hospital birthing facilities. Not all care is evidenced-based, and some care provision may be harmful. Fear prevails among subsets of women and providers. In some settings, medical liability costs are enormous, human resource shortages are common, and costs of providing care can be very high. New challenges linked to alteration of epidemiology, such as obesity and older age during pregnancy, are also present. Data are often not readily available to inform policy and practice in a timely way and surveillance requires greater attention and investment. Outcomes are not equitable, and disadvantaged segments of the population face access issues and substantially elevated risks. At the same time, examples of excellence and progress exist, from clinical interventions to models of care and practice. Labourists (who provide care for all the facility's women for labour and delivery) are discussed as a potential solution. Quality and safety factors are informed by women's experiences, as well as medical evidence. Progress requires the ability to normalise birth for most women, with integrated services available if complications develop. We also discuss mechanisms to improve quality of care and highlight areas where research can address knowledge gaps with potential for impact. Evaluation of models that provide woman-centred care and the best outcomes without high costs is required to provide an impetus for change.

All women should have access to high quality maternity services-but what do we know about the health care available to and used by women? With a focus on low-income and middle-income countries, we present data that policy makers and planners can use to evaluate whether maternal health services are functioning to meet needs of women nationally, and potentially subnationally. We describe configurations of intrapartum care systems, and focus in particular on where, and with whom, deliveries take place. The necessity of ascertaining actual facility capability and providers' skills is highlighted, as is the paucity of information on maternity waiting homes and transport as mechanisms to link women to care. Furthermore, we stress the importance of assessment of routine provision of care (not just emergency care), and contextualise this importance within geographic circumstances (eg, in sparsely-populated regions vs dense urban areas). Although no single model-of-care fits all contexts, we discuss implications of the models we observe, and consider changes that might improve services and accelerate response to future challenges. Areas that need attention include minimisation of overintervention while responding to the changing disease burden. Conceptualisation, systematic measurement, and effective tackling of coverage and configuration challenges to implement high quality, respectful maternal health-care services are key to ensure that every woman can give birth without risk to her life, or that of her baby.

Maternal health is a big issue and is central to sustainable development. Each year, about 210 million women become pregnant and about 140 million newborn babies are delivered-the sheer scale of maternal health alone makes maternal well being and survival vital concerns. In this Series paper, we adopt primarily a numerical lens to illuminate patterns and trends in outcomes, but recognise that understanding of poor maternal health also warrants other perspectives, such as human rights. Our use of the best available evidence highlights the dynamic burden of maternal health problems. Increased diversity in the magnitude and causes of maternal mortality and morbidity between and within populations presents a major challenge to policies and programmes aiming to match varying needs with diverse types of care across different settings. This diversity, in turn, contributes to a widening gap or differences in levels of maternal mortality, seen most acutely in vulnerable populations, predominantly in sub-Saharan Africa. Strong political and technical commitment to improve equity-sensitive information systems is required to monitor the gap in maternal mortality, and robust research is needed to elucidate major interactions between the broad range of health problems. Diversity and divergence are defining characteristics of poor maternal health in the 21st century. Progress on this issue will be an ultimate judge of sustainable development.

In this Series we document the substantial progress in the reduction of maternal mortality and discuss the current state of science in reducing maternal mortality. However, maternal health is also powerfully influenced by the structures and resources of societies, communities, and health systems. We discuss the shocks from outside of the field of maternal health that will influence maternal survival including economic growth in low-income and middle-income countries, urbanisation, and health crises due to disease outbreaks, extreme weather, and conflict. Policy and technological innovations, such as universal health coverage, behavioural economics, mobile health, and the data revolution, are changing health systems and ushering in new approaches to affect the health of mothers. Research and policy will need to reflect the changing maternal health landscape.

On the continuum of maternal health care, two extreme situations exist: too little, too late (TLTL) and too much, too soon (TMTS). TLTL describes care with inadequate resources, below evidence-based standards, or care withheld or unavailable until too late to help. TLTL is an underlying problem associated with high maternal mortality and morbidity. TMTS describes the routine over-medicalisation of normal pregnancy and birth. TMTS includes unnecessary use of non-evidence-based interventions, as well as use of interventions that can be life saving when used appropriately, but harmful when applied routinely or overused. As facility births increase, so does the recognition that TMTS causes harm and increases health costs, and often concentrates disrespect and abuse. Although TMTS is typically ascribed to high-income countries and TLTL to low-income and middle-income ones, social and health inequities mean these extremes coexist in many countries. A global approach to quality and equitable maternal health, supporting the implementation of respectful, evidence-based care for all, is urgently needed. We present a systematic review of evidence-based clinical practice guidelines for routine antenatal, intrapartum, and postnatal care, categorising them as recommended, recommended only for clinical indications, and not recommended. We also present prevalence data from middle-income countries for specific clinical practices, which demonstrate TLTL and increasing TMTS. Health-care providers and health systems need to ensure that all women receive high-quality, evidence-based, equitable and respectful care. The right amount of care needs to be offered at the right time, and delivered in a manner that respects, protects, and promotes human rights.

To improve maternal health requires action to ensure quality maternal health care for all women and girls, and to guarantee access to care for those outside the system. In this paper, we highlight some of the most pressing issues in maternal health and ask: what steps can be taken in the next 5 years to catalyse action toward achieving the Sustainable Development Goal target of less than 70 maternal deaths per 100 000 livebirths by 2030, with no single country exceeding 140? What steps can be taken to ensure that high-quality maternal health care is prioritised for every woman and girl everywhere? We call on all stakeholders to work together in securing a healthy, prosperous future for all women. National and local governments must be supported by development partners, civil society, and the private sector in leading efforts to improve maternal-perinatal health. This effort means dedicating needed policies and resources, and sustaining implementation to address the many factors influencing maternal health-care provision and use. Five priority actions emerge for all partners: prioritise quality maternal health services that respond to the local specificities of need, and meet emerging challenges; promote equity through universal coverage of quality maternal health services, including for the most vulnerable women; increase the resilience and strength of health systems by optimising the health workforce, and improve facility capability; guarantee sustainable finances for maternal-perinatal health; and accelerate progress through evidence, advocacy, and accountability.