Levels of circulating large extracellular vesicles (L-EVs) are increased in individuals with type 1 diabetes mellitus (T1DM) and associated with increased cardiovascular risk. T1DM in pregnancy induces vascular injury leading to adverse maternal and neonatal outcomes. Conversely, exercise has been shown to improve cardiovascular and metabolic health in pregnancy and may represent a non-pharmacological approach to improving pregnancy outcomes. Assessment of vascular health may aid in the identification of individuals at risk of complications and allow for intervention with strategies to improve the maternal vasculature. Unfortunately, there is a paucity of strategies for assessing vascular health in pregnant women. L-EVs are membrane-encapsulated particles released from stressed/injured cells. They are emerging biomarkers of vascular health. The purpose of this thesis was to assess the impact of T1DM and pregnancy on L-EV levels and protein composition, the relationship between L-EVs and pregnancy outcomes and the effect of exercise on L-EV levels. In aim #1, I observed that high levels of L-EVs are predictive of adverse pregnancy outcomes. In aim # 2, I examined the protein composition of circulating L-EVs in hypertensive, diabetic and healthy mice models. Diabetes-enriched proteins were involved in inflammation, SNARE signaling and NAD+ biogenesis. The changes were found in L-EV protein content were consistent with proteins associated with inflammation, cytoskeletal organization, and angiogenesis. Finally, in aim #3, I examined the changes in plasma L-EVs after an acute bout of moderate-intensity aerobic exercise in healthy pregnant and non-pregnant women. I observed that circulating L-EVs significantly decreased after the acute exercise only in non-pregnant individuals. Taken together, my thesis work advances knowledge on L-EVs in T1DM, pregnancy, and hypertension and sets the stage for future work on L-EVs as predictive biomarkers, for molecular profiling, and for monitoring of vascular health interventions in pregnancy.