HDFN Flashcards
List the 3 classes of HDFN
- ABO HDFN
- Rh HDFN
- “Other” HDFN
Msot common class of HDFN
ABO HDFN
Most severe class of HDFN
Rh HDFN
Mechanism of maternal immunization and placental transfer of Ab(s) in HDFN
When baby is born, the placenta breaks and there’s a disruptio of placental circulation and an exchange of maternal and baby blood. The mother makes Abs to the foreign cells
Most common ABO group of a mother who delivers a newborn affected w/ ABO HDFN
Group O
List 3 reasons that a first born child is more likely to be affected w/ ABO HDFN than Rh HDFN
- ABH Ags found widely distributed throughout body
- ABH Ags aren’t fully developed in fetal life
- IgG titer of ABO Abs is usually much lower than anti-D b/c most ABO Abs are IgM; less cross placental and less damage to cells
3 reasons for the severity of Rh HDFN
- Rh is only found on RBCs
- Rh Ags are fully developed at birth
- IgG titer is higher b/c it crosses the placenta
Reasons for the severity of “Other” HDFN
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Reasons for the severity of ABO HDFN
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3 reasons why ABO HDFN is usually a relatively mild disease
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How can fetomaternal ABO incompatibility prevent immunization of the mother against Rh or other blood group Ag
In ABO-incompatible pregnancies, the baby’s RBCs are IMMEDIATELY sensitized by the mother’s ABO abs and are quickly removed from her circulation by her liver
HDFN
- Mechanism of RBC destruction by maternal Ab
Abs are produced as a result of txn or pregnancy. The exposure is usually at the time of the delivery
HDFN
- Response of fetus to RBC destruction
Anemia
HDFN
- Management of bilirubin in utero
Baby’s cells become coated in utero, cells removed by baby’s RES, Hgb breaks down, indirect bili produced, bili removed by moms liver before birth
HDFN
- Management of bilirubin after delivery
After birth, baby’s immature liver canot conjugate bilirubin, so it accumulates in the baby’s system → kernicterus
HDFN
- Greatest danger to the fetus in utero
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HDFN
- Greatest danger to the newborn after delivery
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List 3 indications for performing intrauterine txns (IUTs)
- Amniotic fluid graphs in high zone II or in zone III
- PUBS indicates hgb level < 10 g/dL
- Fetal hydrops is noted on ultrasound exam
What type fo blood should be selected for IUT?
- O neg,
- Washed cells with >80% HCT
- Compatible with mom’s serum
- Ag Neg to mom’s Ab
- “Fresh”
- Irradiated, leukoreduced
- CMV, hgbS Neg
At birth, baby’s blood type may look like ____ ____ b/c 90% of circulation is transfused cells. ____ at birth may be mixed field positive, or possible negative
O negative; DAT
Criteria for cord blood work-up
- Group O
- Rh negative
- IAT +
Cord blood work up
- Weak DAT +
ABO HDFN
Cord blood work up
- Strong DAT +
Rh HDFN
Elution is performed on cord blood to identify ____ coating cell
Ab
HDFN is characterized by what?
Ags absent on maternal RBCs, but present on paternal RBCs
The Ab involved in HDFN can be transported across the placenta b/c it belongs to which Ig class?
IgG
Discuss the pathogenesis of HDFN
- Mother lacks Ag; father has Ag
- Fetus has Ag
- Mom makes Ab after fetomaternal bleed
- Ab crosses placenta in subsequent pregnancies
- Ab coats fetal RBCs
Total bilirubin in the fetal circulation and amniotic fluid may be elevated in HDFN but why is the fetus NOT affected?
Bilirubin gets filtered out by mom’s liver
Which statement is true for ABO HDFN?
- a) It’s generally milder than Rh HDFN
- b) It does not occur in a first pregnancy
- c) The mother is usually blood group O
- d) Phototherapy is often the only treatment required
It doesn’t occur in a first pregnancy
If a neonate requires an exchange txn for HDFN, why is the maternal specimen is the specimen of choice to use for the compatibility test? 2nd choice? 3rd choice?
- 1st: Mom’s serum has highest concentration of offending Ab and therefore, the best sample to test w/
- 2nd: Eluate made from baby’s cells
- 3rd: Baby’s serum
Principle of Liley graph
Plots change in optical density vs. gestational age. Amniotic fluid is measured at 450nm to detect amounts of bilirubin present. Result is plotted and point falls into 1 of 3 zones
Define zones I, II, and III on the Liley graph
- Zones I → mild or no disease
- Zones II → moderate; continue to monitor throughout pregnancy
- Zones III → severe disease, hemolysis; IUT or early delivery
List 3 tests that can detect a fetomaternal hemorrhage
- Weak D
- Rosette test
- Kleihauer-Betke stain
Weak D sensitivity
Least sensitive; requires at least 30mL bleed in order to be detected. Result is weak mixed field
Fetomaternal hemorrhage kit sensitivity
Sensitive to 2mL bleed of fetal cells into mother; appear as rosettes of D+ cells when viewed microscopically
Kleihauer-Betke stain sensitivity
Most sensitive, used to quantify the amount of fetomaternal hemorrhage. Fetal cells appear bright pink, mother’s appear as ghost cells
List the 4 objectives of an exchange txn for a newborn
- To ↓ level of bilirubin and prevent kernicterus
- Remove baby’s sensitized RBCs
- Provide compatible RBCs w/ adequate O2-carrying capacity
- ↓ level of incompatible Ab in baby
Principle of Rosette kit test
Rh+ fetal cells coated w/ anti-D form rosettes w/ Rh+ indicator cells. Distinguished from Rh negative RBCs (qualitative)
Principle of Kleihauer-Betke test
Maternal blood smear treated w/ acid and stained w/ counterstain. Fetal cells resistant to acid remain pink, maternal cells appear as ghosts. After quantitating # of fetal cells present, yield is in % fetal cells
Purpose of ABO/Rh prenatal test
See if mom is group O (predict possibility of ABO/HDFN) and to see if mom is Rh negative, in which she will need antenatal RHIG at 28 weeks
Purpose of IAT prenatal test
Screens for unexpected IgG Abs, those capable fo causing HDFN
Purpose of titer prenatal test
Monitors Ab production in mom. If ↑, corresponds w/ baby affected by HDFN. Indicates need for additional testing, beginning w/ amniocentesis
Purpose of amniocentesis prenatal test
Sample of amniotic fluid is tested fro amount of bilirubin present, plotted on Liley graph
Purpose of Percutaneous Umbilical Blood Sampling (aka cordocentesis)
Takes actual sample of baby’s blood that can be tested for hgb, hct, ABO/Rh, DAT, Ag typing
Purpose of paternal testing
Determine zygosity of father fro offending Ag, thus aiding in predicting occurence of HDFN in baby
Rh Immunge Globulin (RHIG)
- Objective/purpose for administration
Prevent the formation of anti-D in an Rh negative individual who has been exposed to Rh positive RBCs (here, fetal cells) by passive immunization w/ anti-D
Rh Immunge Globulin (RHIG)
- Criteria for candidacy
- Mother must be Rh negative
- Infant must be Rh positive (including weak D)
- Mother must not be already immunized to the D Ag (no anti-D)
- Infants cannot have anti-D coating their cells (DAT+ due to anti-D)
Rh Immunge Globulin (RHIG)
- Indications for use
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Rh Immunge Globulin (RHIG)
- Active ingredient
Sterile IgG anti-D
Rh Immunge Globulin (RHIG)
- Standard dose
300ug neutralizes 30mL WB or 15mL packed cell bleed
Rh Immunge Globulin (RHIG)
- Time frame
Ideally, w/in 72 hours from delivery; better to give late than not at all
Rh Immunge Globulin (RHIG)
- Route of administration
Intramuscularly
Calculate fetal bleed and # of vials RHIG needed
(# fetal cells/total # of cells) x 100 = % fetal cells
% fetal cells x 50 = volume of FMH (WB)
(FMH/30) = # vials + 1
Effects of antenatal RHIG may have on a patient’s IAT results at the time of the delivery
Antenatal dose of RHIG can still be detected in the mother’s circulation at time of delivery (1/2 life of anti-D is 22 days). After confirming recipt of RHIG at 28 week mark, this anti-D can be ignored. Mother will still need another dose of RHIG postpartum. Occasionally, the anti-D from RHIG will coat the baby’s cells giving a DAT+
Rosette
- Positive appearance
- Negative appearance
- Pos: ≥5 rosettes/5 fields (at least 7.5mL fetal bleed into mom)
- Neg: 0-4 rosettes/5 fields (indicates bleed b/w 2.5-7.5mL)
- Neg: 0 rosettes/5 fields (< 2.5 mL fetal bleed into mom)
