Haematolytic disease due to ABO incompatibility: incidence and value of screening in an Asian population.

The population in Singapore is predominantly Asian, with Chinese forming the major ethnic group. The incidence of haemolytic disease of the newborn (HDN) due to Rh incompatibility is very low. The true incidence of HDN due to ABO incompatibility is unknown. Early discharge is practised in Singapore making it important to predict severe HDN due to ABO incompatibility as this would constitute the main cause of haemolysis next to G6PD deficiency. One thousand, six hundred and eight baby-maternal pairs were typed for ABO, Rh, and tested for direct Coombs' test, maternal titre, cord bilirubin and haptoglobin levels. Two hundred and fifty-one were found to be ABO incompatible, with 141 group A and 110 group B babies. The incidence of HDN due to ABO incompatibility was 3.7% of all group O mothers. Coombs' test, maternal antibody titre, cord bilirubin and haptoglobin levels were of low predictive value for severe HDN due to ABO incompatibility. The data further support the notion that it is not cost effective to screen for ABO incompatibility.