Exxcellence pearls: management of pregnancy with ABO incompatibility

Question 1

What is the most common maternal-fetal blood group incompatibility?

What is the most common cause of hemolytic disease of the newborn?

Answer 1

ABO incompatibility

Same

Question 2

Why is intrauterine fetal hemolysis rarely seen with ABO incompatibility?

Answer 2

Naturally occurring anti-A and anti-B antibodies are IgM and thus do not cross the placenta

Question 2

How often is ABO incompatibility seen in newborns?

How does this typically present? Coombs positive or negative?

Answer 2

0.5-1%

Neonatal jaundice due to a Coombs positive hemolytic anemia

Question 3

What maternal and fetal blood types are found with ABO incompatibility?

Answer 3

Maternal blood type O. Fetal blood type A more frequently then type B due to prevalence of these blood types.

Question 4

How would you counsel a patient with a history of ABO incompatibility with hemolytic disease of the newborn?

Answer 4

ABO incompatibility does not demonstrate a consistent pattern. Subsequent newborns may be unaffected or mildly affected. Assessment for intrauterine fetal anemia is not recommended.

Question 5

What percentage of type O mothers have a clinically significant anti-A or anti-B IgG antibodies?

Answer 5

Less than 1%

This is thought to be due to exposure to antigens similar to the A or B antigens such as those found in E. coli.

Question 7

What additional testing should be considered for mothers with type O blood?

Answer 7

Anti-A and anti-B IgG if unexplained fetal anemia is present. Cord blood sample for blood type and antibody testing especially if a previous child had hemolytic disease of the newborn due to ABO incompatibility.