Haemolytic disease of the newborn.

A difference in the proportions of foetal (Hb-F) and adult (Hb-A) haemoglobins between normal infants and those affected by haemolytic disease due to the rhesus factor was first reported by Jonxis (1948). His work was later extended by several investigators and the differences were confirmed. The hitherto reported studies have been concerned mainly with full-term infants and it was the purpose of the present investigation to gain information about the proportions of Hb-F and Hb-A in affected infants born prematurely. As a result we are able to present some original data concerning the problem and to offer an explanation of the results obtained which differs from those previously suggested. Material and Methods Cord blood samples were obtained at delivery from 37 infants affected by haemolytic disease due to the rhesus factor. Cord blood samples were also taken from 29 infants of similar maturities but not affected by haemolytic disease. The samples were analysed for total haemoglobin concentration by the Medical Research Council grey wedge photometry and for Hb-F by the alkali-denaturation method of Singer, Chernoff and Singer (1951). Maturity was assessed clinically and although birth weight was an important factor in assessment the cases were grouped according to the estimated gestational age. Cases delivered during the 35th to 36th week of pregnancy (10 cases) were termed 'premature', during the 37th to 38th week (15 cases) 'pre-term' and after the 38th week (12 cases) 'full-term'. The severity of the haemolytic disease was assessed largely on the cord blood haemoglobin value. A total haemoglobin of 100% (14 8 g./100 ml.) or above placed the infant as 'mildly' affected; if the cord haemoglobin value was 78% (11.5 g./100 ml.) or below the infant was assessed as 'severely' affected. A classification of 'moderate' disease was made if the haemoglobin was between these levels. Clinical condition of the baby, maternal antibody titre and subsequent progress entered