Hypertension is the second most common pediatric chronic disease worldwide. Previous work suggests that an individual’s risk for hypertension could begin in utero. Early seminal studies demonstrated a link between exposure to malnutrition in utero and elevated risk for cardiometabolic abnormalities in the offspring. In the 21st century, studies revealed that hyperglycemia, pre-pregnancy diabetes, and gestational diabetes were all associated with markers of offspring cardiovascular health including increased blood pressure. However, it was not clear whether these associations represented a causal effect. Additionally, it is unclear the extent to which trends in gestational diabetes incidence have changed over time. This thesis was designed to fill these knowledge gaps. First, I conducted a descriptive study of gestational diabetes incidence to assess trends over time and among high-risk groups. Second, to investigate the causal impact of gestational diabetes on youth-onset hypertension among offspring, I conducted a triangulation study. Triangulation in epidemiology refers to conducting multiple studies, all designed to assess the same research question, that have differing limitations, risk of bias, and assumptions. For this thesis I conducted (1) an exact-matched study, (2) a negative exposure control study, and (3) a discordant sibling-matched study. Results showed that diagnosis of gestational diabetes has increased markedly over the last several decades with high-risk groups experiencing the highest rates and lower risk groups experiencing the highest increase in rates. Additionally, the evidence suggests that it is unlikely that exposure to gestational diabetes confers a direct independent increased risk for the development of youth-onset hypertension. Collectively, the work completed for this thesis demonstrates the importance of exploring causal factors that may simultaneously contribute to the cause of both elevated gestational diabetes and elevated youth-onset hypertension.