PROJECT SUMMARY Hypertensive disorders of pregnancy (HDP) are a leading cause of maternal mortality and morbidity in the US, particularly for Black women who are at greatest risk of poor outcomes. In addition to contributions to maternal mortality, HDP increase the risk of chronic hypertension (cHTN), which can lead to cardiovascular (CV) disease. Neighborhood greenspace has been associated with improved CV outcomes in the general population, but few studies have evaluated the relationship between greenspace and the development of HDP and subsequent cHTN. The broad objective of this proposal is to fill this gap by evaluating the impact of greenspace and a greening intervention on HDP and cHTN as well as to determine the utility of greenspace as a racial disparities mitigation tool. We will merge GeoBirth, a cohort that will include 92,000 pregnant patients in Philadelphia, PA from 2008 to 2021, with several neighborhood greenspace datasets, including data from a randomized controlled trial of a greening intervention recently conducted by our team. Our overarching hypothesis is that living near greenspace lowers risk of HDP and cHTN and reduces Black- white racial disparities for these outcomes. We propose the following aims: 1) Observational: To determine if neighborhood greenspace is associated with HDP and cHTN after pregnancy and the extent to which greenspace mediates racial disparities in these outcomes. We will analyze associations of residential greenspace with risk of HDP using multilevel logistic regression adjusted for individual and neighborhood-level confounders (1a). We will determine if greenspace exposure is associated with risk of cHTN within 5 years after pregnancy using survival analysis methods (1b). We will quantify the extent to which higher greenspace exposure among Black women could reduce Black-white HDP and cHTN disparities using causal mediation and interaction analyses (1c). 2) Quasi-experimental: To measure the impact of a neighborhood greening intervention on HDP and cHTN after pregnancy, using a quasi-experimental design. We will analyze the impact of vacant lot greening on risks of HDP and cHTN in the 5 years after pregnancy, using a difference-in- differences analysis of women living near lots that were greened compared to control lots between 2008-2017. 3) Experimental: To examine the impact of a greening intervention on changes in blood pressure during pregnancy, using a previously conducted RCT. We will use data from a completed cluster RCT (2011-2014) vacant lot greening to examine the impact of greening on blood pressure changes (trajectories are associated with development of HDP) from 20 weeks' gestation to delivery, among GeoBirth participants living near 541 vacant lots in three trial conditions: greened lots, trash clean-up only lots, and control lots. The proposed study will be the largest investigation into whether neighborhood greenspace can mitigate HDP risk and cHTN risk after pregnancy and reduce ra...