B-type natriuretic peptide (BNP) and the biologically inactive N-terminal fragment (NT-proBNP) are cardiac hormones collectively known as natriuretic peptides (NPs) that are synthesised and secreted in the ventricular myocardium.1 Serum concentrations are related to left ventricular filling pressures, and can be useful to discriminate between heart failure (HF) and other causes of breathlessness.2 Concentrations are higher in untreated or decompensated HF and fall after treatment.3 Therefore, NPs are a useful marker of cardiac function and treatment response. Here, NPPB is linked to hydrops fetalis.