GDF15 and hydrops fetalis: GDF‐15 is secreted from the myocardium in response to various stimuli such as ischaemia, wall stress, or pressure overload.17 It is also secreted from fibroblasts in response to stress stimuli.18 Thus, although the mechanisms are still unclear, both cardiomyocytes and heart fibroblasts could be the source of GDF‐15 in patients with HF.