Fetal hemoglobin contains

The blood of the human fetus normally contains fetal hemoglobin (hemoglobin F). Its structure is similar to that of hemoglobin A except that the b chains are replaced by g chains; that is, hemoglobin F is a2g2. The g chains have 37 amino acid residues that differ from those in the b chain. Fetal hemoglobin is normally replaced by adult hemoglobin soon after bihRef: Ganong&;s Review of medical physiology 25th edition. Page: 557