What is hemoglobin F? Why does the fetus need a different hemoglobin?
Hemoglobin F is the hemoglobin found in the mammalian fetus and hemoglobin A is the normal hemoglobin. Hemoglobin F has higher affinity for oxygen.
The fetus needs hemoglobin capable of extracting oxygen from the mother's circulation. Thus the fetus uses hemoglobin F as it has higher affinity for oxygen than the mother's hemoglobin.
The Circulatory System - Image Diversity: hemoglobin F