<unk> , or foetal<unk>  (also<unk>  F,<unk> , or α2γ2) is the main oxygen carrier protein in the human fetus.<unk>  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 and the levels remain high after birth until the baby is roughly 2–4 months old.<unk>  F has a different composition from the adult forms of<unk> , which allows it to bind (or attach to) oxygen more strongly. This way, the developing fetus is able to retrieve oxygen from the mother's bloodstream, which occurs through the placenta found in the mother's uterus. In the newborn, levels of<unk>  F gradually decrease and reach adult levels (less than 1% of total<unk>  usually within the first year, as adult forms of<unk>  begin to be produced. Diseases such as beta thalassemias, which affect components of the adult<unk> , can delay this process, and cause<unk>  F levels to be higher than normal. In sickle cell anemia, increasing the production of<unk>  F has been used as a treatment to relieve some of the symptoms.
Fetal hemoglobin
Hemoglobin
Ferritin
Beta-2 transferrin
Mean corpuscular hemoglobin
Indoxyl sulfate
Fetal fibronectin
Neopterin