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Fetal Hemoglobin (Hemoglobin F)
Fetal hemoglobin (hemoglobin F)
is the main hemoglobin that carries oxygen around the body of the developing baby during the last 7 months of pregnancy.
Fetal hemoglobin is best suited to the conditions in the womb and the oxygen transport needs of babies before they are born.
A few weeks before birth the baby starts to make increasing amounts of adult hemoglobin (hemoglobin A). Hemoglobin A is better suited to the oxygen transport needs after birth and throughout adult life. After birth the baby makes less and less hemoglobin F and more and more hemoglobin A.
Hemoglobin F does not turn into hemoglobin A.
Hemoglobin F and hemoglobin A are completely different hemoglobins.
Hemoglobin is made up of 4 proteins chains and a "heme" group that contains iron. Hemoglobin F is made up of 2 alpha chains and 2 gamma (fetal) chains. Hemoglobin A is made up of 2 alpha chains and 2 beta (adult) chains.
As they grow babies automatically turn off the production of hemoglobin F and turn on the production of hemoglobin A- It takes about 2 years for a baby to completely switch over to adult hemoglobin.
A baby who makes normal fetal hemoglobin will not necessarily be able to make normal adult hemoglobin.
Sickle cell disease is caused by an abnormal adult hemoglobin, called hemoglobin S. People with sickle cell disease make hemoglobin S instead of hemoglobin A.
Newborn babies with sickle cell disease make hemoglobin F and hemoglobin S. Most babies (who don't have sickle cell disease) make hemoglobin F and hemoglobin A.
Babies with sickle cell disease experience more problems as hemoglobin F is turned off. Most people with sickle cell disease made normal hemoglobin F as babies.
Hydroxyurea, one of the new drugs used to treat sickle cell disease in adults works by turning hemoglobin F back on.
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