<prompt> Affinity of fetal Hemoglobin to oxygen is more than adult hemoglobin due to:2, 3 BPG in bloodDecreased pHIncreased pCO2Right shift  <response>: a. 2, 3 BPG in bloodRef: Nelsons 20e p 2336, Ghai 8e p 345Greater affinity of fetal Hb for oxygen is explained by lack of fetal Hbs interaction with 2,3-bisphosphoglycerate 2,3-BPG or 2,3-DPG; In adult red blood cells, 2,3 DPG decreases the affinity of hemoglobin for oxygen2,3-BPG interacts less efficiently with fetal hemoglobin than adult hemoglobin, due to a change in a single amino acid residue 143 found in the 2,3-BPG binding pocket: from histidine to serine, leading to greater oxygen affinity. 