ABO haemolytic disease: sex ratio and blood groups in the newborns requiring treatment.

In our group of newborns we have observed that the rate of occurrence of incompatibility states between blood group 0 mothers and their blood group A or B offspring amounted to 14%. It was in every tenth newborn that this incompatibility became manifest as a haemolytic disease requiring treatment. There were no significant differences between blood group A or B newborn infants, either in the frequency rates of hyperbilirubinaemia or in the uniformly indicated therapeutical measures. Among the neonates treated successfully by phototherapy boys prevailed significantly. In contrast, among the most severe forms of the ABO haemolytic disease, requiring blood exchange transfusion, there was a significantly higher prevalence of girls. In relationship to the time of institution of phototherapy as a method of treatment, there occurred a significant decrease of the rates of newborns treated by exchange transfusion. This was due specially to a significant decrease of the necessity of performing this procedure in blood group A boys.