Project Summary Stillbirths and neonatal deaths are two adverse birth outcomes of critical global health relevance. In 2021, an estimated 1.9 million babies were stillborn, and 2.3 million liveborn babies died before reaching 28 days of age. Sub-Saharan Africa (SSA) stands out globally as the world region having the largest number of stillbirths and neonatal deaths (respectively 847,000 and 1,067,000 in 2021). These large numbers not only reflect large population sizes, but also high levels of stillbirth and neonatal mortality in the SSA region. Moreover, not only are neonatal mortality rates high in countries of the SSA region relative to other world regions, but in many SSA countries, they are high relative to the country’s own levels of postneonatal mortality. This indicates the existence in many SSA populations of a distorted age pattern of mortality at early ages with excess mortality at neonatal ages, impeding their ability to meet Sustainable Development Goals targets. In spite of the significance of these patterns, measurement and understanding of stillbirth rates and neonatal mortality in SSA countries are hindered by major gaps in data availability and quality. Undercount of stillbirths and neonatal deaths as well as misclassification of neonatal deaths vs. stillbirths in existing, mostly retrospective sources remain major concerns. Issues with availability and quality of information on preterm, low birthweight and small for gestational age – three major risk factors that can play a large role in both levels and age patterns of early-age mortality – are additional gaps that further impede proper monitoring of patterns of mortality during the late fetal and neonatal periods in the SSA region. The goal of this project is to improve our understanding of why many SSA populations stand out globally in terms of both their levels and age patterns of mortality during the late fetal and neonatal periods by collecting new prospective data in three surveillance sites located in three different SSA countries (Ethiopia, Gambia and Guinea-Bissau), covering a variety of contexts. While the focus of this project is on three SSA populations located in Ethiopia, Gambia and Guinea- Bissau, results will have methodological and substantive implications for other low-income countries, including other SSA countries, which are characterized by a high burden of stillbirths and neonatal mortality as well as large data gaps in their stillbirth and neonatal mortality information.