Protocols for testing newborns vary internationally and within countries.
If the mother is D negative and has no unexpected antibodies, newborns are always tested at delivery.
Some labs do not test all newborns if the mother is Rh positive and especially do not test if the mother is a blood group other than group O. If all infants born to Rh positive women were tested, many positive DATs due to ABO incompatibility would be detected that are of no clinical significance. Instead cord blood is retained for a period of time (eg, 7 days), should it be needed. (It may be needed if the mother has an unexpected antibody at delivery or if the newborn develops signs of red cell hemolysis.)
However, some clinical practice guidelines, such as those of the American Academy of Pediatrics specify that testing infants born to group O Rh-positive mothers is optional only if there is appropriate surveillance and risk assessment before discharge and provided there is follow-up.
Not testing becomes an issue if group O women and their infants are discharged within 24 hours as occurs in some locations, since hyperbilirubinemia due to ABO HDFN may develop later. Therefore, some facilities where early discharge occurs require that all infants born to group O Rh positive mothers be tested.
Typical protocols:
- Infants born to Rh negative mothers are tested;
- Infants born to Rh positive mothers who are group O are often tested, especially if early discharge is common (limiting surveillance);
- Infants born to Rh positive mothers who are not group O are often not tested and this is acceptable practice. Cord blood is typically retained for a period should it be needed for testing later.
