Anemia of Prematurity - Portal Neonatal

• Serologic tests
Imaging Studies:
o Indirect Coombs test and direct antibody test (DAT) results are positive in the mother
and affected newborn. The maternal titers are the highest dilution of maternal serum
at which a positive agglutination test result is obtained. Unlike Rh alloimmunization,
DAT results are positive in only 20-40% of infants with ABO incompatibility. This is
because fetal RBCs have less surface expression of type-specific antigen compared
to adult cells.
o Although the indirect antiglobulin test result (neonate's serum with adult A or B RBCs)
more commonly is positive in neonates with ABO incompatibility, it has poor predictive
value for hemolysis. This is because of the differences in binding of IgG subtypes to
the Fc receptor of phagocytic cells and, in turn, in their ability to cause hemolysis.
o IgG2 is more commonly found in maternal serum but has weak lytic activity, which
leads to the observation of little or no hemolysis with a positive DAT result. On the
other hand, significant hemolysis is associated with a negative DAT result when IgG1
and IgG3 are predominant antibodies, which are in low concentration but have strong
lytic activity, crossing to neonatal circulation.
Table 1. Comparison of Rh and ABO Incompatibility
Clinical aspects
Laboratory
findings
Characteristics
Rh ABO
First born 5% 50%
Later pregnancies More severe
Stillborn/hydrops Frequent Rare
Severe anemia Frequent Rare
Jaundice
Moderate to severe,
frequent
No increased
severity
Mild
Late anemia Frequent Rare
DAT Positive Weakly positive
Indirect Coombs
test
Positive Usually positive
Spherocytosis Rare Frequent
• Perinatal ultrasonography: High-resolution ultrasonography has been a major advance in
detection of early hydrops, and it has also reduced the fetal trauma and morbidity rate to less
than 2% during percutaneous umbilical blood sampling (PUBS) and placental trauma during
amniocentesis. High-resolution ultrasonography has been extremely helpful in directing the
needle with intraperitoneal transfusion (IPT) and intravascular transfusion (IVT) in fetal
location.