<prompt> Non immune hydrops fetalis is caused byHIVCMVHSVParvovirus B 19  <response>: Primary fetal infection is associated with nonimmune fetal hydrops and intrauterine fetal demise,with the risk for fetal loss after infection estimated at 5. The mechanism of fetal disease appears to be a viral-induced RBC aplasia at a time when the fetal erythroid fraction is rapidly expanding ,leading to profound anemia, high-output cardiac failure, and fetal hydrops. Nonimmune type Three major causes -- parvovirus B 19 -- alfa-thalassemia -- cardiovascular defects, chromosomal anomalies, and fetal anemia Reference: Nelson textbook of pediatrics 19th edition, Page 1096 