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ABO Hemolytic Disease of the Fetus and Newborn

(A) Apple, (B) Bee, (O) Owl Blood Cells with Fetus Lysing RBC's
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ABO Hemolytic Disease of the fetus and newborn is caused by ABO incompatibilities between the mother and fetus or newborn. This can occur when the mother has O type blood while the fetus has type A or B. The mother will produce anti-A or anti-B antibodies which attack fetal/neonatal red blood cells resulting in hemolytic anemia. This disease is most often asymptomatic, but can also present as neonatal jaundice. Diagnostically, a Coombs test will be negative or weakly positive. Management is primarily with phototherapy, but transfusion may be necessary.
8 KEY FACTS
CHARACTERISTICS
ABO Incompatibilities
(A) Apple, (B) Bee, (O) Owl Blood Cells with Incompatible-X

ABO incompatibilities are present in ~20% of all pregnancies, however only 5-10% of newborns are symptomatic. The highest risk is with type O mothers and type A or B newborns.

Type O Mother and Type A/B Fetus
(O) Owl Pregnant-woman and (A) Apple with (B) Bee Fetus

The highest risk for ABO incompatibility involves blood type O mothers and blood type A or B newborns.

Anti-A or Anti-B Antibodies
Anti-tie (A) Apple or Anti-tie (B) Bee with Ant-tie-bodies

The presence of pre-existing maternal antibodies (anti-A or anti-B IgG) are able to cross the placenta and can result in hemolysis in the fetus. As these pre-existing antibodies are present even if sensitization has not occurred, hemolysis can commence even during the first pregnancy.

Hemolytic Anemia
Hemolyzing-RBCs from Anemone

Neonatal hemolytic anemia can occur due to the hemolysis of RBCs in the fetus. The anti-A or anti-B antibodies from the mother may cross the placenta and start binding to fetal RBCs, tagging them for lysis. Overall though, ABO incompatibility usually has a significantly milder course of disease compared to Rh incompatibility.

PRESENTATION
Often Asymptomatic
Thumbs-up

ABO hemolytic disease often presents asymptomatically, but if the number of lysed RBCs is significant, findings like anemia, hyperbilirubinemia, and jaundice may occur.

Neonatal Jaundice
Newborn Jaundice-janitor

Mild neonatal jaundice can present at birth or within 24 hours after birth.

DIAGNOSIS
Negative Coombs Test
Negative Comb

If there are signs of hemolysis postnatally, a Coombs test can be conducted. ABO incompatibilities will have a mostly negative or weakly positive Coombs test because macrophages will phagocytose most antibody-bound RBCs so very little agglutination occurs.

MANAGEMENT
Phototherapy
Photo-flash

Postnatal treatment includes phototherapy and, if necessary, transfusion with RBCs can be used to address hyperbilirubinemia. Additionally, iron supplementation can ameliorate the symptoms of neonatal hemolytic anemia.

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