A massive Swedish registry analysis of 4.17 million births found that maternal psychiatric disorders diagnosed before delivery increased offspring cardiovascular disease risk by 19% over 51 years of follow-up. The association was particularly pronounced for heart failure, with a 59% increased risk. Even after controlling for familial confounding through cousin comparisons, the elevated risk persisted at 8% overall and 51% for heart failure. Congenital heart disease mediated nearly 10% of this association, while preterm birth and low birth weight contributed minimally. This finding adds compelling evidence to the growing body of research on intergenerational health transmission, suggesting that maternal mental health may influence fetal cardiovascular development through biological mechanisms beyond shared genetics or lifestyle factors. For clinical practice, this supports enhanced cardiovascular monitoring for children of mothers with psychiatric histories. However, as a preprint awaiting peer review, these results require validation. The observational design also limits causal inference, though the cousin comparison strengthens the evidence. This appears to be an incremental but meaningful contribution to understanding how maternal health shapes long-term offspring outcomes.