PTEN and hydrops fetalis: To further explore the role of AKT signalling in WIH-A and WIHN, we developed both Lgr5+ cells deletion and Pten knockout mice model, and the result shows that Lgr5+ HF stem cells have an important function in both WIH-A and WIHN, and elevated AKT (Pten loss) signalling in Lgr5+ HF stem cells promotes WIHN.