In inverse variance weighted (IVW) MR, we identified at a false discovery rate (FDR) of 5% nineteen blood proteins that were significantly associated with HF (ABO, BAG3, FLT4, TDGF1, FUT3, FSTL1, ALDH3A1, GLCE, PTHLH, CDON, FCGR2A, RGMB, AMH, MIF, IL15RA, B3GAT3, CCDC126, ST3GAL6, APOA5) (Fig. 1) (Suppl. The gene discussed is FCGR2A; the disease is hydrops fetalis.