PDGFA and hydrops fetalis: However, it is well‐established that HF formation and growth involves different conserved signaling pathways including, but not limited to, Wnt/β‐catenin, Sonic hedgehog (Shh)/PDGF‐A, FGF, BMP, TGF‐β, and Edar/nuclear factor‐kappa B (NF‐κB) pathways.