Hydrops fetalis d/t Hb ba is associated with?

- Hydrops fetalis is seen in most severe form of a-thalassemia, caused by deletion of all four a-globin genes. - Hb in these fetus have tetramers of g-globin chains (hemoglobin Bas) which have high affinity for oxygen. - This results in decreased delivery of oxygen to the tissues. - Survival in early development of these fetus is d/t expression of z chains, an embryonic globin that pairs with g chains to form functional z 2 g 2 Hb tetramer.