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. Rh compatibility causes massive red blood cell destruction, which leads to several problems, including total body swelling. Severe swelling can interfere with how the body organs work. Nonimmune Hydrops fetalis occurs when a disease or medical condition disrupts the body's ability to manage fluid. There are three main causes for this type: heart or lung problems, severe anemia (thalassemia), and genetic defects, including Turner syndrome. The exact cause depends on which form a baby has.