REN and hydrops fetalis: HF, heart failure; NT-proBNP, n-terminal brain natriuretic peptide; HFrEF, heart failure with reduced ejection fraction; HFmrEF, heart failure with mid-range ejection fraction; HFpEF, heart failure with preserved ejection fraction; BNP, brain natriuretic peptide; AA, aldosterone antagonist; BB, beta blocker; RASi, renin-angiotensin system inhibitor.