Although these results mainly reflect jaundice due to ABO incompatibility, the two infants with haemolysis not caused by ABO also had very high aUCB; the only infant with proven Rhesus-incompatibility disease had the highest aUCB recorded in the study period at 113.9μmol/l, and the infant with G6PD manifesting as early jaundice had an aUCB of 51μmol/l, on the 99th centile of our data. The gene discussed is ABO; the disease is Jaundice.