ENDOGENOUS FORMATION OF CARBON MONOXIDE IN NEWBORN INFANTS III. ABO Incompatibility

Summary The carboxyhaemoglobin (COHb) concentration in blood, which is assumed to reflect the degree of haemoglobin catabolism, was determined in 62 newborn infants selected because of significant jaundice associated with ABO incompatibility, and in 46 infants with ABO incompatibility, selected without regard to the degree of bilirubinaemia. Furthermore, the COHb level was determined in 46 icteric infants without haemolytic disease, and in 61 infants of ABO homospecific pregnancies, selected without regard to their bilirubin level. In infants with ABO incompatibility increased COHb concentrations were found not only in infants with unequivocal signs of haemolytic disease but also in infants with a clinical picture indistinguishable from physiological jaundice. During the first days the relation between COHb and bilirubin in infants with ABO incompatibility was the same, whether the infants were selected because of significant jaundice or irrespective of the degree of bilirubinaemia. This indicates a common pathogenesis of the bilirubinaemia in the two groups. The COHb and bilirubin levels in infants of ABO heterospecific pregnancies and in infants of ABO homospecific pregnancies, selected without regard to the degree of bilirubinaemia, were compared. It is concluded that the COHb level probably is a more sensitive indicator of haemolysis than the bilirubin concentration. Increased COHb concentrations were also found in icteric infants without blood group incompatibility, but the relation between COHb and bilirubin indicates that in ABO incompatibility increased haemolysis is of greater importance in the pathogenesis of the jaundice.