Objective: This study explores the relationship between Life's Essential 8 (LE8) score and gestational diabetes mellitus (GDM), subsequent diabetes, and mortality, and analyzes the mediating effects of platelet-related indicators and inflammatory markers. Methods: The study utilized cohort, data from the Nutrition Examination Survey (NHANES), applying logistic regression models and mediation effect analysis to assess the associations between LE8 score and GDM. Potential confounding factors such as age, race, education, PIR, health insurance, and access to healthcare were adjusted to ensure the reliability of the results. Linear mediation analysis, conducted using the "mediation" package with 1000 bootstrap replications, quantified the mediating roles of mean platelet volume (MPV), white blood cell (WBC), and lymphocyte (LYM) counts. Results: We analyzed data from the NHANES from 2007 to 2018, involving 59,842 participants. Among them, 858 had a history of GDM. Each unit increase in LE8 score reduced GDM odds by 3%. High Cardiovascular health (CVH) individuals exhibited 70% lower GDM risk versus low CVH. WBC (5.8%), LYM (4.8%), and MPV (0.6%) partially mediated LE8-GDM associations, highlighting inflammation's mechanistic role. High LE8 scores predicted 94% lower diabetes risk post-GDM. Mortality analysis revealed a U-shaped association between LE8 scores and mortality risk, with borderline evidence of nonlinearity (P = 0.069). Conclusion: As the first study to integrate CVH metrics with platelet/inflammatory biomarkers in GDM pathogenesis, our findings demonstrate that optimizing LE8 scores, particularly through BMI, blood pressure, and lipid control, significantly mitigates GDM risk and complications. Integrating LE8 assessment at first prenatal visit may enable early risk stratification and personalized interventions.