Non immune hydrops fetalis is caused by

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