HDN Maternal Perspective Flashcards
HDN definition
Maternal alloantibodies specific for inherited paternal RBC antigens, resulting in fetal/newborn RBC destruction
When do fetal RBCs sensitize mom?
- trauma
- delivery
- medical interventions
- aborted pregnancies
Test to run if HDN suspected
DAT
detects if Ab already attached to baby RBC
What alloantibody does Type O mom make against Type A or Type B baby? Can it cause HDN?
anti-A,B IgG
Can cause HDN
Test to run if DAT positive for HDN suspicion
Elution Ab ID
Traits of HDN Ab
- can cross placenta (IgG)
- not absorbed by normal tissues
- causes hemolysis (IgG1 and IgG3 more efficient)
- positive on fetal cells
Follow-up test if positive Ab ID
Ab titer
Describe Ab titer results if HDN is happening
Ab titer gets stronger in the presence of sensitizing baby Ag
List order of maternal testing
- ABO Type and screen
- Ab ID
- Ab titer if positive Ab ID
- FMH qualitative screen
- KLB or flow cytometry quantitative test
What information is gathered when diagnosing HDN?
- transfusion and pregnancy history
- type and screen
- confirm rh neg status for rhogam
- Ab ID if needed
- Ab titration baseline
Critical titer for anti-D
16-32 in AHG phase
Critical titer for anti-K
8
Significant change defined by a difference of what dilution?
2-fold dilutions
As long as the titer is less than ____, titers may be performed every 4-6 weeks
8
As little as _____ of fetal cells can sensitize mom
1 ml
95% cases diagnosed before 1968 were because of ____
D antigen
Serological detection of Weak D
- IS And AHG phase
- polyclonal anti-D
- verify with saline control
- if mutation inside RBC membrane, then don’t need Rhogam (Weak D) bc mom won’t make anti-D
Describe Rhogam protection
One dose protects mom against D-pos exposure of 30 ml bleeds for up to 12 weeks
Molecular Weak D testing
SNP panel for Weak D, run on MALIDI-Tof or other automated genotype analyzer
When to do molecular weak D testing
- woman childbearing age is weak D
- woman of childbearing age is Rh pos but has anti-D serologically demonstrated
Weak D tests mostly done for who?
Babies and donors
not moms
What is Rhogam?
High-titered IgG anti-D that immunizes D-neg mom against D Ag
Criteria for receiving Rhogam
- Rh-neg mom
- Mom no history of anti-D
Describe antepartum Rhogam dosing
- Initial dose at 28 wk gestation
- Dose follows invasive procedures amniocentesis or cordocentesis
- Dose can also follow pregnancy manipulations (abortion)
Describe postpartum Rhogam
Give within 72 hr of delivery of Rh-pos infant
Fetal maternal bleed (FMH) screen test principle
- Weak anti-D reagent incubates with pt cells, wash away unbound Ab, incubate with indicator cells to form countable rosettes
- dependent on fetus being Rh pos and mother Rh neg
FMH test results
- qualitative test to determine dose of RhIG
- Neg result means < 15 ml bleed, give standard dose
- Pos result means > 15ml bleed, perform quantitative test to find dose
Kleihauer-Betke test principle
Fetal hemoglobin resistant to acid treatment and will stain darker than maternal cells
Kleihauer-Betke calculation for number of RhIG doses
- % bleed = #fetal cells/#mom cells
- doses = %bleed * (5000/30) + 1
- # mom cells = 1000
Kleihauer-Betke purpose
Determine extent of fetal bleed
T/F
Fetus must be Rh pos to have bleed detected in Kleihauer Betke test
False
Can be Rh neg
Fetal neonatal alloimmune thrombocytopenia
- IgG plt antibodies cross placenta
- 80% caused by anti-HPA-a1
- IVIG therapy treatment
- Mom’s anti-plt antibodies attack baby’s platelets
Immune thrombocytopenic purpura (ITP)
- Autoimmune disorder in mom, can also affect fetus
- body attacks own platelets
- 15% neonates need plt transfusion at birth
- treat w Prednisone
Most common cause of HDN
ABO
