Management of pregnancy when maternal blood has a very high level of fetal haemoglobin

Summary. Fetal blood normally has a higher oxygen affinity than maternal blood because of the predominance of haemoglobin (Hb) F in the former and of Hb A in the latter; this predominance facilitates the transfer of oxygen from maternal to fetal blood. We report two patients who had exclusively or predominantly Hb F in their blood and were managed differently. When patient 1 became pregnant she had regular exchange blood transfusions in order to reduce her Hb F from 80% to below 50%; patient 2, who had 100% Hb F, was not transfused before, during or after her pregnancy. Each patient delivered a normal healthy baby. We conclude that the differential oxygen affinity produced by the combination of Hb A in the maternal blood and Hb F in the fetal blood is not indispensable to ensure an oxygen supply adequate for normal fetal development and growth.