ABSTRACT Severe maternal morbidity (SMM), which encompasses conditions that put pregnant people most at risk of dying (e.g., hemorrhage, sepsis, organ failure), doubled in the last two decades. The most common precursors to SMM – anemia, hypertensive disorders of pregnancy (HDP), and cesarean birth – are also increasing. People of color, especially Black and Native American people, are at increased risk for all these outcomes. This Renewal proposal builds on our prior work to address inequities in maternal outcomes. Via the Parent Grant, our team enhanced current understanding of the contribution of social context (focusing on neighborhood social disadvantage) and maternal pre-pregnancy health (focusing on body mass index) to SMM risk, using a unique data resource we built of California (CA) births. This Renewal uses theoretically grounded approaches to address several remaining gaps in our understanding of maternal health in the U.S. that were illuminated by the Parent Grant. We will build a unique resource of 16 million births in three states from 1997-2021. The dataset longitudinally links vital records (live birth and fetal death certificates) with hospital discharge data for mother and baby; includes residential address; and links data for repeat pregnancies to the same person over time, thus providing the type of large-scale data with high-quality information on maternal health and social context that the field needs to advance population-level research on maternal health. All phases of the research will be guided by a community advisory board (CAB). Using an intersectionality framework, Aim 1 will examine joint impacts of multiple forms of marginalization on SMM, its subtypes (i.e., hypertension-, hemorrhage-, and sepsis-related SMM), and its precursors (i.e., HDP, anemia, mode of birth). Indicators of marginalization include race-ethnicity, education, health care payer, nativity, and census tract-level markers of social disadvantage and structural inequality (e.g., poverty, segregation). Using a reproductive life-course framework, Aim 2 will determine the cumulative impact of social and medical risk factors across successive pregnancies on maternal health (i.e., SMM, SMM subtypes, SMM precursors). We will examine how factors related to social context (e.g., persistent census tract poverty), morbidity (e.g., persistent HDP), and mode of birth (primary cesarean birth) affect subsequent occurrence and recurrence of the study outcomes. Aim 3 will use findings from Aims 1 and 2 to identify and prioritize strategies to improve maternal health and equity. We will use a) causal inference methods (mediation and g-computation) to understand mechanisms and compare the potential impact of selected hypothetical interventions on study outcomes and disparities, and b) community-engaged prioritization methods to synthesize our findings and prioritize next steps. By understanding risks across multiple forms of marginalization and successive pregnancies, a...