"In 2011, an estimated 3 million children died in their first four weeks of life. The majority of these neonatal deaths are avoidable if effective low-cost interventions, such as clean delivery practices, exclusive breastfeeding, and newborn resuscitation are available. However, these interventions are clearly not reaching many of the women and newborns who need them most. A major challenge is how best to expand access to essential obstetric and newborn interventions, particularly among disadvantaged populations and in areas with poor access to health services. This requires an understanding of the social and geographical patterning of neonatal mortality rates (NMR) as well as evidence about which policies can reduce inequalities in access to essential maternal and newborn care. The three objectives of my thesis addressed these issues directly.First, we described socioeconomic inequalities in NMR across low- and middle-income countries (LMIC) and assessed changes in inequalities over the past decade. Using Demographic and Health Survey (DHS) data from 24 countries, we estimated absolute and relative socioeconomic inequalities using the Slope Index of Inequality and the Relative Index of Inequality, respectively. In most countries, absolute and relative inequality in NMR declined over the approximate 10-year period. There was, however, considerable heterogeneity both in the magnitude of NMR inequalities between countries and in how inequalities changed over time. Furthermore, there remained a substantial survival advantage for newborns born into wealthier and more educated households, which should be considered in global efforts to further reduce NMR. Next, we evaluated the impact of a policy that removes user fees for facility-based deliveries on health service utilization, neonatal mortality, and socioeconomic inequalities. Using DHS data from ten countries in sub-Saharan Africa, we employed a difference-in-differences regression approach to control for underlying secular trends in the outcomes that are common across countries and for time invariant differences between countries. Reducing fees for delivery services was associated with an increase in facility-based deliveries and a possible reduction in NMR. Furthermore, increases in facility-based deliveries occurred across all socioeconomic groups, with no indication that richer or more educated women benefited more from the policy change.Finally, we assessed the effect of distance to emergency obstetric and newborn care (EmONC) services on early neonatal mortality and examined whether proximity to services contributed to socioeconomic inequalities in early neonatal mortality. Using geographical coordinates collected in both surveys, we linked data from the 2011 Ethiopian DHS with comprehensive facility census data from the 2008 Ethiopian EmONC Needs Assessment. Closer proximity to delivery services and higher level of care were associated with lower early NMR. Distance to EmONC services was a main determinant of total inequality in NMR, although it did not make a significant contribution to socioeconomic inequality. In this thesis, we have identified several barriers that contribute to large and persistent inequalities in neonatal mortality and in the utilization of essential obstetric and newborn care in LMIC. The findings highlight the importance of a multipronged policy approach that addresses geographic accessibility and quality of obstetric and newborn services, affordability barriers, and socioeconomic inequalities to significantly reduce neonatal mortality. Further research examining the relative importance of various access barriers in different settings will help policy makers and planners adopt locally relevant approaches to improve newborn survival." --