Ba's hydrops fetalis is lethal because:
Hb Ba: Most severe form of Alpha thalassemia As Hb Ba's consists of 4-gamma chains - have very high oxygen affinity Thus, it cannot release oxygen to fetal tissues.
Hb Ba's cannot bind oxygen
The excess a-globin form insoluble precipitates
Hb Ba's cannot release oxygen to fetal tissues
Microcytic red cells become trapped in the placental
Hemolytic anemia