GDF15 and hydrops fetalis: However, further research is required, as it is not precisely known whether GDF-15 is a consequence or the source of these pathophysiological processes, especially since its serum levels are also correlated with those of matrix metalloproteinases (MMP), which are essential molecules in changing the architecture of ECM due to collagen degradation and turnover, with a subsequent impact on LV stiffness, geometry, and the progression of HF [33].