Tests on newborn (mandatory if the mother is Rh negative):
- ABO and Rh*
- Mandatory: Test for weak D if initial Rh typing appears to be D-negative
- DAT**
*ABO typing of the infant does not require a reverse serum group with A1 and B cells since the newborn is not expected to have anti-A or anti-B (unless of maternal origin).
*If cord blood is used for ABO and Rh(D) typing, the red cells should be washed very well to remove possible Wharton's jelly.
**A positive DAT does not indicate the newborn has clinically significant hemolysis. For example, a positive DAT commonly occurs due to ABO incompatibility, yet infants seldom require treatment. Also, infants born to mothers who received antenatal RhIG sometimes have a positive DAT that does not cause clinically relevant hemolysis.
Also note that policies for DAT testing of newborns whose mothers have received antenatal RhIG vary internationally. For example, the British Committee for Standards in Haematology guidelines state that a DAT should not be performed on cord blood routinely since it may be positive due to antenatal RhIG prophylaxis. A DAT is recommended only if HDFN is suspected because of a low cord blood hemoglobin or the presence of unexpected maternal antibodies.
In North America, DATs are always performed on infants born to Rh-negative mothers who are RhIG candidates.
