Fœtal Hæmoglobin and Erythroblastosis

THE hæmoglobin of the fœtus and the new-born child and the hæmoglobin of older children and adult people can be distinguished by their different resistance against 0·1 N sodium hydroxide. At pH 12 normal hæmoglobin is denatured very rapidly, whereas foetal hæmoglobin is denatured only slowly. By using this difference in denaturating-rate, it is possible to calculate the amounts of foetal and later hæmoglobin present in small samples of blood1. A normal new-born child has only fœtal hæmoglobin. During the early months after birth, this hæmoglobin is gradually replaced by later hæmoglobin, at a rate of a little less than 1 per cent a day, so that after 120 days normally all foetal hæmoglobin has disappeared. In prematurely born babies, later hæmoglobin appears only at the time that the child ought to have been born2.