Fetal hemoglobin

Fetal hemoglobin
(4 subunits, α2γ2)
Structure of fetal hemoglobin (HbF). The 2α and 2γ subunits are in red and yellow, respectively, and the iron-containing heme groups in green. From PDB: 4MQJ​, by authors Soman, J. and Olson J.S.
Protein type	metalloprotein, globulin
Function	oxygen-transport
Cofactor(s)	heme (4)
Subunit name Gene Chromosomal locus Hb-α1 HBA1 Chr. 16 p13.3 Hb-α2 HBA2 Chr. 16 p13.3 Hb-γ1 HBG1 Chr. 11 p15.4 Hb-γ2 HBG2 Chr. 11 p15.4

Fetal hemoglobin, or foetal haemoglobin (also hemoglobin F, HbF, or α₂γ₂) is the main oxygen carrier protein in the human fetus. Hemoglobin F is found in fetal red blood cells, and is involved in transporting oxygen from the mother's bloodstream to organs and tissues in the fetus. It is produced at around 6 weeks of pregnancy ^[1] and the levels remain high after birth until the baby is roughly 2–4 months old.^[2] Hemoglobin F has a different composition than adult forms of hemoglobin, allowing it to bind (or attach to) oxygen more strongly; this in turn enables the developing fetus to retrieve oxygen from the mother's bloodstream, which occurs through the placenta found in the mother's uterus.^[3]

In the newborn, levels of hemoglobin F gradually decrease and reach adult levels (less than 1% of total hemoglobin) usually within the first year, as adult forms of hemoglobin begin to be produced.^[4] Diseases such as beta thalassemias, which affect components of the adult hemoglobin, can delay this process, and cause hemoglobin F levels to be higher than normal.^[5] In sickle cell anemia, increasing the production of hemoglobin F has been used as a treatment to relieve some of the symptoms.^[6]