Rh Incompatibility and Newborn Transfusions

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Questions and Answers

What percentage of D-negative mothers became immunized following pregnancy before the use of RhIg?

50%

20%

13%(16%) (correct)

1-2%

What is the purpose of post-partum administration of RhIg?

To detect fetal hemoglobin in maternal circulation

To prevent sensitization of D-negative mothers (correct)

To quantify the number of fetal red blood cells in maternal circulation

To diagnose jaundice in newborns

What is the name of the test used to confirm the presence of fetal hemoglobin in maternal circulation?

Rh antibody test

Acid elution test

Kleihauer-Betke test (correct)

Flow cytometry

What is the purpose of exchange transfusions in newborns?

To transfuse compatible red blood cells to the newborn Signup and view all the answers

What is the result of the removal of the complex (RhIg + fposRBCs) by macrophages in the mother's spleen?

The removal of fetal red blood cells from the mother's circulation Signup and view all the answers

What is the purpose of prenatal screening for HDN?

To identify D-negative mothers at risk of sensitization Signup and view all the answers

What is the effect of post-partum administration of RhIg on the percentage of D-negative mothers becoming immunized following pregnancy?

It reduces the percentage to 1-2% Signup and view all the answers

What is the newest confirmatory test used to quantify the number of fetal red blood cells in maternal circulation?

Flow cytometry Signup and view all the answers

Why is only Rh-negative blood transfused to Rh-negative females of childbearing potential?

To prevent Rh incompatibility Signup and view all the answers

What is the most antigenic RBC antigen?

D Signup and view all the answers

What happens to the hemoglobin liberated from damaged RBCs?

It is metabolized to indirect bilirubin Signup and view all the answers

What is a consequence of Kell antigen incompatibility?

Severe anemia due to destruction of circulating RBCs and precursors Signup and view all the answers

Why is prenatal screening for hemolytic disease of the newborn (HDN) important?

To detect Rh incompatibility Signup and view all the answers

What is the consequence of Rh incompatibility in a fetus?

Hemolytic disease of the newborn Signup and view all the answers

What is the role of anti-D in prenatal screening?

To detect Rh incompatibility Signup and view all the answers

What is the result of hemolysis of RBCs in a fetus?

Release of heme, globin, and iron Signup and view all the answers

Why does the mother produce an antibody of the IgG class?

Because IgG is the only antibody that can cross the placenta Signup and view all the answers

What is the significance of the father being homozygous or heterozygous in Rh incompatibility?

It determines the percentage of HDN in the second child Signup and view all the answers

What happens when anti-D antibodies cross the placenta and encounter the D antigen on the fetal red cells?

The anti-D antibodies destroy the fetal red cells Signup and view all the answers

What is the consequence of fetomaternal hemorrhage during pregnancy?

It increases the risk of HDN in the second child Signup and view all the answers

What is the requirement for the development of Rh incompatibility?

The mother must lack the Rh antigen Signup and view all the answers

What is the consequence of the reaction between anti-D antibodies and the D antigen on the fetal red cells?

It destroys the fetal red cells Signup and view all the answers

Study Notes

Rh Incompatibility and HDFN

13% of D negative mothers became immunized following pregnancy, but post-partum administration of RhIg reduced this to 1-2%.
Addition of antepartum administration of RhIg further reduced the percentage.

Newborn Transfusions

Blood transfused to the newborn after delivery is not the same as uterine transfusion.
Newborn infant may receive small aliquot transfusions or exchange transfusions, or both.
The newborn infant receives RBCs in the maternal circulation, which can be detected using the KLEIHAUER BETEKE test (acid elution test).

RhIg and Antibody Production

RhIg binds to fetal RBCs in the maternal circulation, and the complex is removed by macrophages in the spleen.
The RBC antigens are thus removed, and the mother produces an antibody of the IgG class.
IgG is the only antibody that can cross the placenta, which is why it's produced in response to Rh incompatibility.

HDFN

HDFN occurs when the mother lacks the antigen and the fetus has the antigen (e.g. Rh negative mother and Rh positive fetus).
The mother produces an antibody (anti-D) that can cross the placenta and destroy the fetal RBCs.
The reaction between anti-D and the D antigen on the fetal RBCs causes hemolysis (HDN).

Factors Affecting Immunization and Severity

Antigen exposure, particularly fetomaternal hemorrhage during pregnancy, can cause significant increases in maternal antibody titers and increase the severity of HDN.
Father's genotype affects the risk of HDN, with homozygous fathers conferring a 100% risk and heterozygous fathers conferring a 50% risk.

Other Antigens and Causes of HDN

Other antigens in the Rh system, such as C, E, and c, are also potent immunogens, although less than D.
Kell antigens are present on immature erythroid cells in the bone marrow, and can cause severe anemia.
Other causes of HDN include anti-Fyᵃ, anti-Leᵃ, anti-s, and others.

Hemolysis and Indirect Bilirubin

Hemolysis releases hemoglobin, which is metabolized to indirect bilirubin.
Indirect bilirubin is transported across the placenta and can cause jaundice in the newborn.

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Description

This quiz covers the resolution of Rh incompatibility, including the percentage of D negative mothers who became immunized following pregnancy, and the use of RhIg to prevent sensitization. It also touches on newborn transfusions.