TM HDFN (Hemolytic Disease Of Fetus and Newborn) Flashcards
What is HDFN ?
maternal red cell antibodies (IgG) cross placenta and attach to fetal cells = hemolysis
Which blood groups cause Severe vs Mild HDFN ?
Severe: Rh, Kell, Duffy, Kidd
Mild: ABO, Duffy
Tests done as part of prenatal screening
ABO Rh, Antibody screen
Who gets RhIg and when ?
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
Serological work up for HDFN
Infant:
- ABO Rh
- DAT
Mother:
- Ab screen
- Fetal bleed screen (if Rh pos child w/ Rh neg mother)
Symptoms of fetus in HDFN
- anemia
- increased erythropoiesis aka “Erythroblastosis fetalis”
- severity depends on antibody ID and concentration
Factors of maternal Ab production (5)
- 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
Symptoms in severe cases of HDFN (in utero)
- profound anemia
- hepatosplenomegaly
- hypoproteinemia
- cardiovascular failure (heart enlarged bc decrease in RBC mass)
- “Hydrops fetalis” severe edema = infant dies in utero
Symptoms in severe cases of HDFN (postpartum)
- anemia
- hyperbilirubinemia = unconjugated bilirubin increases = KERNICTERUS
- hemolysis continues postpartum
NOTE: unconjugated bilirubin crosses blood-brain barrier = brain damage
why don’t we see jaundice in fetus ?
Bilirubin in amniotic fluid is excreted by mom; jaundice only seen in newborn since fetal liver is underdeveloped
most common blood group associated with HDFN
ABO !
- but MILD or subclinical anemia (no jaundice but increased bilirubin)
- first pregnancy can be affected
Purpose of RhIg
used to prevent anti-D production in pregnancy when given to Rh neg females
T or F: RhIg can be given even when active anti-D is present
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
Pre-natal testing follow-up when Ab screen is positive
- Ab ID with panel
- perform titration
- antigen type mother and father
What titre is significant for IgG antibodies ?
Titre of ≤16
Any titre of this blood group is significant
anti-K causes SEVERE HDFN
What to do with a positive DAT ?
- Elution
- ID Ab using panel
Fetal bleed screen
- “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)
Kleihauer Betke test
- 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
Partial elution : what is it and what can be used ?
“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
What is an exchange transfusion ? Why is it done ?
- 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
If ABO Rh cord is = Rh neg but wk D pos, should the mother be given RhIg ?
Yes, mothers of weak D fetus is STILL ELIGIBLE for RhIg