Hemolytic Disease of the Fetus and Newborn

Define hemolytic disease of the newborn

A disorder of the fetus or newborn in which the fetal red blood cells are destroyed by maternal IgG antibodies

The time period before birth is called?

Prenatal/Antenatal

The time period within the first 28 days after birth is called?

Neonatal

Parity (Para) refers to what?

Number of live births

Gravidity (grava) refers to what?

Number of pregnancies

What is Hydrops fetalis?

In HDN, as fetal hemolysis occurs cardiac output increases leading to cardiac failure and fluid accumulation in abdomen

Discuss the role of the placenta during pregnancy

The placenta acts as the site of gas, nutrient, and waste exchange between mother and the fetus

ABO HDN happens when mother is ___ and baby is ___

O

A or B

State the three elements needed for HDN to occur

1. The mother must make an IgG antibody to a foreign RBC antigen

2. The fetus must possess the antigen the IgG antibody targets

3. The antigens must be well developed at birth

Which HDN is more severe: ABO or Rh?

Rh

State the 3 theories of why ABO HDN is less severe than Rh HDN

• Presence of A or B substances in fetal tissues that neutralize maternal antibodies

• Poor development of ABO antigens in prenatal period

• Reduced number of ABO antigens in prenatal period

Describe the mechanism of action of RhIG

A recent theory involves the production of specific cytokines that work to suppress a primary immune response in the mother to positive fetal red blood cells.

List two antibodies commonly implicated in HDN that are not Anti-ABO or Anti-D

They must be in IgG class

Ex.

Anti-c

Anti-K

What testing during the initial prenatal visit?

• ABO/D

• Antibody screen (for IgG antibodies)

• Antibody titer (if screen is positive)

What testing should be done 26-28 weeks gestations?

Confirm D-typing

Repeat antibody screen

If a clinically significant antibody was identified (in a pregnant person), how often should an antibody titer be performed?

every 4 weeks

An antibody titer of __ is considered significant enough to cause HDN

32

What maternal testing should be done postpartum?

ABO/D Typing

Antibody Screen

Antibody ID

Fetal screen (Rosette)

Kleihauer-Betke

What infant testing should be done postpartum?

ABO/D typing ( Only forward typing because babies don’t have antibodies)

DAT

Elution

What is the blocking phenomenon as it relates to the D-antigen in cord blood?

The infant is falsely typed as Rh negative BECAUSE the mothers anti-D is covering the infants antigens —>

this blocks reagent Anti-D from agglutinating cells

A sample experiencing the blocked D phenomenon will type as Rh ____ and essentially always have a ____ IgG DAT

Negative

Positive

One dose of RhIG covers ___mL of D-positive blood

30

<1 rosette per 3 hpf. how many doses of RhIG?

1 dose

Determine the number of RhIG units needed when provided a case study

Always round up if at a 0.5 limit

Define exchange transfusion

Complete blood volume transfusion needed for severe cases of HDN

What are the requirements for blood products used in exchange transfusions?

Blood products must be:

• Group O (or ABO compatible) D negative blood

• RBC <7 days old suspended in fresh frozen plasma to HCT of 45-60%*

• CMV-reduced products

• Irradiated

• Hemoglobin S negative

• Blood must lack the antigen to maternal antibody

• Compatible crossmatch with maternal serum