NPPB and hydrops fetalis: Endpoints spanned functional (6MWD), biochemical (NT-proBNP), and hard events: factor 4 [13] predicted time-to-event (HR 1.51, 95% CI 1.21-1.90), whereas phenylalanine [15] predicted incident HF hospitalization (HR 1.29; replicated HR 1.23) and improved continuous NRI by 0.21, a population-level classification gain that may not translate directly to clinical HF cohorts.