Congenital hydrops fetalis describes an abnormal accumulation of fluid in two or more compartments in a fetus. The disease is categorized based on the aetiology: immune- and non-immune hydrops fetalis. Today, the nonimmune form is the most common. Once born, the child is initially handled symptomatically and will often needintensive care and treatment. Even though approximately one in five cases is still idiopathic, genetic diagnostictools have become increasingly important in the diagnostic process. The prognosis depends on the aetiology andthe gestational age when diagnosed and at birth, as argued in this review.