<prompt> Ba;s hydrops fetalis is lethal becauseHb Bas cannot bind oxygenThe excess a - globin form insoluble precipitatesHb Bas cannot release oxygen to fetal tissuesMicrocytic red cells become trapped in the placental  <response>: Ba hydrops fetalis is a lethal complication of alpha thalassemia trait where oxygen can;t release from hemoglobin. Hb Bas is formed of 4 gamma chains. The oxygen affinity is so high that it releases very little oxygen into the fetal tissues. Reference: Ghai essential of pediatrics, eighth edition, p.no:342 