In normal fetal development, two types of alpha-globin genes (HBA1 and HBA2) are responsible for producing the alpha-globin chains that form part of hemoglobin. In Hemoglobin Bart's hydrops fetalis, all four alpha-globin genes are deleted or mutated, leading to the absence of functional alpha-globin chains. This results in the formation of hemoglobin Bart's, which has a high affinity for oxygen but is ineffective at releasing it to tissues, causing severe tissue hypoxia.
