Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hydrops fetalis ?
    ### Response:
    Hydrops fetalis is a serious condition in which abnormal amounts of fluid build up in two or more body areas of a fetus or newborn. There are two types of hydrops fetalis: immune and nonimmune. Immune hydrops fetalis is a complication of a severe form of Rh incompatibility.
    