GREM1 and hydrops fetalis: Immunostaining score of Grem1 expression in cardiomyocytes continued to increase in the stages C/D HF group, where the highest value of this score was observed, comparing this Grem1 immunostaining score to the control (p < 0.001), stage A HF (p < 0.001), and stage B HF groups (p < 0.001).