1. Carry out ABO and Rh grouping of the mother and infant.
There can be no Rhesus incompatibility caused by anti-D antibody unless the mother is Rh negative and the infant is Rh positive.
occasionally, when grouping the infant’s
cells they may not appear Rh positive when antigen D receptors on the baby’s cells have been coated with maternal anti-D.
3. Measure the infant’s haemoglobin and serum bilirubin
2. Carry out a DAT test on the infant’s cord cells. The DAT will be positive in Rhesus HDN.
4. Examine a Romanowsky stained blood film for the features of HDN, including spherocytosis which is usually less marked than in ABO HDN, polychromasia (reticulocytosis) and many nucleated red cells.
With Rhesus HDN, the infant’s haemoglo-
bin is usually below 140 g/l (14 g/dl) and the serum unconjugated bilirubin may rise to over 340 µmol/l (20 mg%). Such high levels of unconjugated bilirubin can cause irreversible brain damage (kernicterus).
5. Test also the mother’s serum for anti-D antibody when this has not been tested previously.
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