Modified Project Summary/Abstract Section Project 2 The prevalence of cardiovascular disease (CVD) has continued to climb among US women, despite greater prevention efforts. Pregnancy may provide an understudied window into a woman’s long-term cardiovascular health. Normal physiological adaptations to support a fetus can act as a stressor on a woman’s body, potentially uncovering or exacerbating underlying chronic conditions. Cardiovascular-related complications, such as preeclampsia and hypertension, may have persistent effects into the postpartum period and have been related to elevated CVD risk in later life. Moreover, environmental exposures such as air pollution have been associated with altered maternal blood pressure and lipid homeostasis, while psychosocial stressors may independently influence maternal health by increasing inflammation and risk of prenatal hypertensive disorders. Efforts to understand the roles of both the environment and psychosocial stress in prenatal cardiovascular complications and long-term maternal health risks may be most critical among individuals who experience combined impacts of multiple social, physical, and environmental stressors, which may exacerbate health risks. Despite growing evidence of the impact of such exposures on maternal cardiovascular health during pregnancy, there is little to no research available on whether environmental exposures and social stressors during the prenatal period may enhance a mother’s cardiovascular risk in the postpartum period and into later life. Even less is known about the mechanisms underlying these effects in the postpartum context, but recent studies support a key role for miRNAs in both pregnancy and in risk of CVD and suggest that these epigenetic regulators can be modulated by environmental exposures. We propose to investigate whether prenatal traffic-related and ambient air pollution exposures increase maternal postpartum cardiovascular effects in 500 women in the MADRES cohort, a prospective pregnancy cohort. We will accomplish this by the following specific aims: (1) investigate the impact of air pollutants and social stressors during pregnancy on trajectories of cardiovascular risk factors in the first four years postpartum and examine whether these effects vary by pregnancy-related complications and individual-level factors; and (2) determine the role of cardiovascular-related miRNA in prenatal air pollution-related associations in cardiovascular health trajectories in the first four years postpartum, and test whether they mediate these associations and examine their functional relevance. These results may shed light on the contribution of environmental and social stressors to CVD risk factors in the postpartum period and could be critical for identifying women at greater risk of developing chronic disease in later life.