Clinical Significance

The cord blood sample, being comparatively large in volume, is the ideal specimen for screening for hemolytic disease of the newborn, (HDN). The maternal sample collected routinely for Rh testing provides good material for further investigation when the direct coombs (DAT) is positive.

The IgG antibodies that cause ABO hemolytic disease nearly always occur in the mother's circulation without a history of prior exposure to human red cells and can occur in an pregnancy including the first. It is restricted almost entirely to group A or B infants born to group O mothers. The Rh antibodies, primarily anti-D and the other IgG antibodies such as Kell, Fy, etc. require sensitization either in previous pregnancies, blood transfusions, or from maternal hemorrhage during pregnancy. The fetus is passively immunized, but at birth the fetal concentration of IgG usually exceeds the maternal level. When fetal cells are sensitized by maternal antibody, they are removed from circulation by the reticulo-endothelial system, resulting in varying degrees of severity. Cell destruction casuses anemia, which in early life may cause heart failure, liver and spleen stress. Extremely elevated bilirubin levels can cause brain cell damage or death.