HF is one of the most serious types of cardiovascular diseases, including atherosclerosis, cardiac fibrosis, and hypertrophy, which were all correlated with IL-33 and ST2 because IL-33 binding to ST2 not only leads to maladaptive pro-hypertrophic but also causes pro-fibrotic responses to mechanical stretch and stress (although IL-33 treatment reduces hypertrophy and fibrosis, sST2 prevents anti-hypertrophic effects of IL-33) [23, 24]. Here, IL33 is linked to hydrops fetalis.