Lecture 11 - HDFN

List 2 conditions that must be met for HDFN to occur.

mother must have an IgG antibody in sufficient quantity to cross the placenta and cause red cell destruction

infant must have the corresponding antigen inherited from the father.

What is the most serious PRENATAL problem associated with HDFN?

anemia

Why is bilirubinemia not a problem until after birth?

During pregnancy

Why is anemia such a problem?

If there are not enough red cells the baby will try to compensate which can lead to heart failure and death.

Why is bilirubinemia such a problem?

If the bilirubin gets too high it deposits into baby's brain causing kernicterus leading to damage ranging from deafness

Define erythroblastosis fetalis.

nucleated RBCs in peripherial circulation

Define icterus gravis.

severe jaundice

Define kernicterus.

rapid increase in unconjugated bilirubin in the brain resulting in brain damage

Define hydrops fetalis.

generalized edema caused by cardiovascular failure

What are the most common antibodies involved in HDFN?

ABO. They are pre-existing and can occur with the first pregnancy.

Why is anti-D HDFN more severe than ABO HDFN?

The D antigen is fully developed before birth

What is the worse case scenario for ABO HDFN and why?

O mom w/A or B baby. Mom has anti-A

Does ABO or Rh HDFN have more spherocytes?

ABO. The cells are almost all completely destroyed with anti-D.

What is the DAT for ABO?

weak to negative

What is the DAT for anti-D HDFN?

strong

The mother is B neg and has a negative antibody screen. The baby is B pos and has a positive DAT. What kind of HDFN are we talking about and how would you prove it?

The mother has an antibody to a low-incidence antigen which the baby inherited from the father. Test the mother's serum (if ABO compatible with the father) and the baby's eluate (should have antibody) against father cells and the reaction should be positive.

Mom is B positive with positive antibody screen and baby is O negative with a positive DAT? What antibody could be coating the baby cells?

Infant is O so it is not an ABO antibody, mom is D positive so it is not anti-D

Most common HDFN antibodies other than ABO/D are anti-K and anti-c but it could be any of the other IgG antibodies. It cannot be either anti-Lea or Leb since babies are Le(a-b-). What tests are done on a mom for her first prenatal workup?

ABO/D typing

When is a titer considered insignificant?

A titer for an IgG antibody is always significant in a pregnant woman. However

Why do we run titers in parallel with the previously tested sample?

Different technique (shaking

What does the Color Doppler Middle Cerebral Artery Peak Systolic Velocity measure and what is it used for?

It measures how fast the fetus' blood is flowing. The faster the flow

What is a cordocentesis?

It is a high risk procedure that can obtain or deliver blood directly from or into the umbilical blood vessel.

For what substance is an amniocentesis testing?

Bilirubin giving a measure of the degree of hemolysis

At what optical density is the bilirubin measured?

The ∆OD (delta OD) is measured at 450 nm.

How is the Liley graph used to measure the bilirubin?

The optical density (OD) is plotted on the Liley graph and measured at 450 nm to determine how much danger the baby is in. The graph has been divided into three zones

What is an intrauterine transfusion (IUT) used for?

To provide antigen negative cells to baby (no lyse). Provides more oxygen carrying cells which would be increased with the new cells.

What is the difference between an intraperitoneal IUT (intrauterine transfusion) and intravascular IUT?

Intraperitoneal IUT places the red cells directly into the peritoneal cavity of the infant and the cells are taken up by the lymphatic ducts intravascular IUT puts the cells directly into the umbilical vein (percutaneous umbilical blood transfusion).

What are the two most important determinants in whether to perform an exchange transfusion or not?

The bilirubin level and/or how fast it is rising and the cord hemoglobin which can tell you how anemic the fetus is.

What is the single most important serological test in the diagnosis of HDFN after birth?

DAT

Mom is an O pos and has an anti-K. The baby is B pos with a 1+ DAT. The baby's eluate is as follows: A1 cells - 0, B cells - 1+, I cell - 0, II cell - 0, III cell - 0. What antibody(ies) is (are) most likely causing the problem?

anti-B from the mother

if it were due to anti-A

B

If the B cells tested in the baby's eluate are positive, why is anti-B not implicated in the HDFN?

Mom is an A pos with anti-Jka. Baby is a B pos with a 2+ DAT. The eluate reacts as follows: A1 cells - 2+, B cells - wk+, O cells I

In theory, how could you prove the anti-B vs anti-Jka on the B cells?

What is the purpose of an exchange transfusion?

Since the greatest danger post-delivery is the increased bilirubin

What is the purpose of phototherapy?

The UV light will decompose the bilirubin into a non-toxic substance which can be excreted by the baby.

What are the requirements for a woman to be a candidate for RhIg?

36. She must be D negative

Why is RhIg only used to prevent anti-D HDFN?

RhIg is a 300 μg vial of purified anti-D. It prevents the formation of anti-D only. The other antigens do not cause HDFN often enough to warrant the development of an immune globulin for each of them.

What is the dosage for Rh immune globulin?

1 vial of RhIg will neutralize a 30 ml whole blood bleed in a fetal-maternal hemorrhage (fetus will bleed whole blood) or 15 ml of D positive RBCs (not whole blood packed cells) transfused to a D negative patient.

Why is an O negative mother with an ABO incompatible D positive infant considered to be at a decreased risk of developing anti-D if she didn't get RhIg as compared to an A negative mother with an O positive infant?

The anti-A

Mom is in the hospital to deliver her second child. She is a B R1r with an anti-E. If Dad is an O R1R1, do we need to worry about HDFN?

Mom is an O pos with anti-Fya. The baby is an A pos with a 2+ DAT. The eluate is as follows: A1 cells - 2+, B cells - 1+, O cells (III)

What is the principle of the Rosette test?

If the fetus has bled into the mother, these D positive indicator cells attach to the anti-D on the fetal D positive cells and form a "rosette" around the Rh positive fetal cells which are visible microscopically.

What is the principle of the Kleihauer-Betke test?

Fetal hemoglobin is resistant to acid elution adult hemoglobin is not. The cells are smeared onto a slide which is placed in an acid bath to denature the adult hemoglobin. The slide is stained and the fetal cells appear as bright pink cells while the adult cells appear as "ghost" cells.

If the Kleihauer-Betke is negative, does this mean the mother is not a candidate for Rh immune globulin?

How many units of RhIg do you need to give to a mother if you count 43 fetal cells on the Kleihauer-Betke test?

108 mL bleed

If a D negative adult received a 200 cc unit of D positive red cells, how many vials of RhIg would this individual need to receive to remove the D positive cells?

What is the normal time limit for administering RhIg?

However if the anti-D has not formed yet, how many weeks old is the fetus when RhIg is given antenatally (before birth)?

72 hours; 28

If the mother is an R1R1 and the father is an Ror, what antibodies could the mother make that could affect the fetus? Mom is an O. R1r and Dad is an A R2R2. What antibodies could the mother make with this father that would affect the fetus?

Mom is a B R2Ro, Dad is an A R1r

What chemical can be used to distinguish between an IgG or IgM anti-D in a recently delivered D negative mother who did received RhIg?

2-ME or DTT will destroy an IgM antibody. Add some to the serum and repeat the test. If it is a primary response IgM antibody

If Mom is O negative with a negative antibody screen and the newborn is A positive with a positive DAT, what is the MOST LIKELY antibody on the baby's cells?