This paper shows that poor health at birth can act as a barrier to upward economic mobility, reinforcing inequality across generations. Using linked administrative data for two Canadian birth cohorts, we find that mothers born with low birth weight (LBW) are significantly more likely to have LBW children. Sibling comparisons reveal that LBW reduces the probability of surpassing parental income rank by 4 percent. We show that ongoing childhood health shocks partly—but not fully—explain this effect, suggesting both direct and indirect pathways. Our findings highlight how policies targeting prenatal and early-life health could help break persistent cycles of disadvantage.