TGFB1 and hydrops fetalis: Furthermore, this process is tightly regulated by multiple signaling pathways, including the Wnt/β-catenin pathway, which promotes HF initiation and growth [18,19]; the BMP signaling pathway, involved in cell fate determination [20,21]; the SHH signaling pathway, which regulates morphogenesis [22]; the Notch signaling pathway, affecting stem cell maintenance and differentiation [23,24]; and the transforming growth factor TGF-β family, which is extensively involved in regulating cellular behavior [25].