TM HDFN (Hemolytic Disease Of Fetus and Newborn)

Question 1

What is HDFN ?

Answer 1

maternal red cell antibodies (IgG) cross placenta and attach to fetal cells = hemolysis

Question 2

Which blood groups cause Severe vs Mild HDFN ?

Answer 2

Severe: Rh, Kell, Duffy, Kidd
Mild: ABO, Duffy

Question 3

Tests done as part of prenatal screening

Answer 3

ABO Rh, Antibody screen

Question 4

Who gets RhIg and when ?

Answer 4

Rh neg women WITHOUT ACTIVE anti-D:
1. 28 weeks gestation
2. If mother gives birth to Rh pos OR weak D child = <72 hours post-delivery

Question 5

Serological work up for HDFN

Answer 5

Infant:
- ABO Rh
- DAT
Mother:
- Ab screen
- Fetal bleed screen (if Rh pos w/ Rh neg mother)

Question 6

Symptoms of fetus in HDFN

Answer 6

• anemia
• increased erythropoiesis aka “Erythroblastosis fetalis”
• severity depends on antibody ID and concentration

Question 7

Factors of maternal Ab production (5)

Answer 7

• amount of blood exposure (0.5 mL vs 25 mL)
• immunogenicity of antigen (D vs Fya)
• previous exposure (primary vs secondary)
• maternal immune response (responder vs. non-responder)
• ABO compatibility

Question 8

Symptoms in severe cases of HDFN (in utero)

Answer 8

• profound anemia
• hepatosplenomegaly
• hypoproteinemia
• cardiovascular failure (heart enlarged bc decrease in RBC mass)
• “Hydrops fetalis” severe edema = infant dies in utero

Question 9

Symptoms in severe cases of HDFN (postpartum)

Answer 9

• anemia
• hyperbilirubinemia = unconjugated bilirubin increases = KERNICTERUS
• hemolysis continues postpartum

NOTE: unconjugated bilirubin crosses blood-brain barrier = brain damage

Question 10

why don’t we see jaundice in fetus ?

Answer 10

Bilirubin in amniotic fluid is excreted by mom; jaundice only seen in newborn since fetal liver is underdeveloped

Question 11

most common blood group associated with HDFN

Answer 11

ABO !
- but MILD or subclinical anemia (no jaundice but increased bilirubin)
- first pregnancy can be affected

Question 12

Purpose of RhIg

Answer 12

used to prevent anti-D production in pregnancy when given to Rh neg females

Question 13

T or F: RhIg can be given even when active anti-D is present

Answer 13

FALSE; RhIg CANNOT BE GIVEN when active anti-D is present
- it’s a prevention strategy so if it’s made… can’t remove it

Question 14

Pre-natal testing follow-up when Ab screen is positive

Answer 14

• Ab ID with panel
• perform titration
• antigen type mother and father

Question 15

What titre is significant for IgG antibodies ?

Answer 15

Titre of ≤16

Question 16

Any titre of this blood group is significant

Answer 16

anti-K causes SEVERE HDFN

Question 17

What to do with a positive DAT ?

Answer 17

• Elution
• ID Ab using panel

Question 18

Fetal bleed screen

Answer 18

• “Rosette test”
• detects if >30 mL Rh pos fetal cells entered maternal circulation
• done on MATERNAL SAMPLE 1 hr after delivery
• if mother is eligible for RhIg (Rh neg) ; FBS will be performed
• positive result = additional RhIg is required (NOT COMMON)

Question 19

Kleihauer Betke test

Answer 19

• QUANTIFIES how much Rh pos blood has entered maternal circulation
• determines how many extra doses of RhIg is required

NOTE: THIS HAS BEEN REPLACED BY FLOW CYTOMETRY

Question 20

Partial elution : what is it and what can be used ?

Answer 20

“Dissociation” removes Ab so antigens on RBCs can be typed
- EGA; but destroys Kell antigens
- CDP
- ZZAP/ WARM; but papain destroys MNS, Duffy and DTT destroys Kell
- modified heat @ 45°C

Question 21

What is an exchange transfusion ? Why is it done ?

Answer 21

• small amount of newborn’s blood is removed and replaced with donor whole blood [Hct = 0.55]
• corrects anemia
• reduces newborn [bilirubin]
• removes sensitized cells and unbound maternal Ab

Question 22

If ABO Rh cord is = Rh neg but wk D pos, should the mother be given RhIg ?

Answer 22

Yes, mothers of weak D fetus is STILL ELIGIBLE for RhIg