The findings of HF signal pathways in humans and mice indicates that the Wnt [39], TGF-β [40], MAPK [41], Shh [42], Notch and JAK-STAT [43] pathways widely participate in every part of the HF cycle, development, and morphogenesis, and greatly contribute to all kinds of HF. The gene discussed is SHH; the disease is hydrops fetalis.