<prompt> Non-immune hydrops fetalis is caused by all exceptParvo B19 virusChromosomal abnormalitiesalpha-thalassemiaABO incompatibility  <response>: Immune hydrops fetalis is caused by red blood cell alloimmunisation haemolytic disease. All other causes are described as non-immune hydrops fetalis NIHF. Hydrops is a symptom of a wide range of conditions which have resulted in an imbalance in fetal fluid between the vascular and interstitial space.Diagnostic criteria are fluid in at least two body cavities pleural space, pericardial space, peritoneal space, skin or placental enlargement. The prognosis depends on associated prematurity, the underlying cause, the severity of any associated pulmonary hypoplasia and the severity of the ongoing post-natal fluid accumulation. Reference: GHAI Essential pediatrics, 8th edition 