HDFN Flashcards
the destruction of the red blood cells (RBCs) of a fetus and neonate by antibodies produced by the mother
HDFN
95% of the cases of HDFN were caused by maternal antibodies directed against the
RhD
The mother can be stimulated to form RBC antibodies naturally (ABO), by
previous pregnancy, or transfusion
(RBC alloimmunization)
initial diagnosis of maternal RBC alloimmunization is
Serologic
reported a transfusion reaction from transfusing a husband’s blood to a postpartum woman
1939 Levine and Stetson
the mother had been immunized to the fa- ther’s antigen through
fetomaternal hemorrhage (FMH). The antigen was later identified as RhD.
caused by the destruction of the fetal RBCs by antibodies produced by the mother.
HDFN
Only antibodies of the immunoglobulin _____ class are actively transported across the placenta via Fc receptors
IgG
In the case of HDFN
the antibodies are directed against the blood group antigens on the fetal RBCs that were inherited from the father.
the most common cause of HDFN
HDFN Caused by ABO
are present in the plasma of all individuals whose RBCs lack the corre- sponding antigen
isohemagglutinins / ABO Abs
most likely to form high-titered IgG anti-ABO antibodies, ABO HDFN is nearly always limited to A or B infants of_______ with potent anti- A,B antibodies.
Group O mother
mild course of ABO HDFN
related to the poor development of ABO antigens on fetal RBCs
The serious conse- quences seen with other causes of HDFN, such as
-still birth
-hydrops fetalis
-kernicterus
ABO HDFN causes a bilirubin peak at
1 to 3 days
the leading cause of maternal alloimmunization.
Fetomaternal Hemorrhage
Interventions that can increase the risk of FMH.
amniocentesis
chorionic villus sampling
trauma to the abdomen
active transport of IgG begins in the
Second trimester
IgG molecules are transported via the
Fc portion
more efficient in RBC intravascular he- molysis than are IgG2 and IgG4
IgG 1 and IgG3
common antigens in the Rh system
C, E, c
is considered the most clinically significant in its ability to cause HDFN.
Anti-Kell
present on immature erythroid cells in the fetal bone marrow, so severe anemia occurs not only by destruction of circulating RBCs but also by destruc- tion of precursors
Kell antigens
occurs when maternal IgG attaches to specific antigens of the fetal RBCs
Hemolysis
Destruction of fetal RBCs and the resulting anemia stimulate the fetal bone marrow to produce RBCs at an accelerated rate
Erythroblastosis fetalis
the development of high-output cardiac failure with generalized edema, effusions, and ascites, a condition known as
Hydrops fetalis
Hydrops fetalis can develop
18 to 20 weeks
three different phases of anemia caused by HDFN
early (within 7 days of birth)
- due to antibody- mediated hemolysis;
late hemolytic anemia (2 weeks or more after birth)
- due to continued hemolysis, the expanding intravascular compartment, and natural decline of hemoglobin levels;
late hyporegenerative anemia
- due to marrow suppression as a result of transfusions and IUT, antibody destruction of RBC precursors, and deficiency of erythropoietin
Onset : Within 7 days of birth
Mechanism : Antibody-mediated hemolysis
Bilirubin : Elevated
Reticulocyte count : Normal or high
Early-onset anemia
Onset : >/= 2weeks
Mechanism:
1. Antibody-mediated hemolysis
2. Natural decline of Hb levels
3. Expanding intravascular volume of growing infant
Bilirubin : usually elevated
Reticulocyte count: Normal to High
Late hemolytic anemia
Onset : >/= 2 weeks
Mechanism:
1. Antibody destruction of RBC precursors and RBCs
2. Marrow suppression by IUT and transfusions
3. Erythropoietin deficiency
4. Expanding intravascular volume of growing infant
Bilirubin: Normal
Reticulocyte count: Low or Absent
Late hyporegenerative anemia
bilirubin can reach levels toxic to the infant’s brain
more than 18 to 20 mg/dL
newborn develops jaundice
12 - 18 hours
most important diagnostic testing HDFN cause by ABO
DAT on the cord or neonatal RBCs
recommended practice is to perform in HDFN Caused by RBC Alloimmunization
type and antibody detection test at the first prenatal visit, preferably during the first trimester.
must be able to detect clinically significant IgG alloantibodies that are reactive at 37°C and in the anti- globulin phase.
antibody detection method, or indirect antihuman globulin test (IAT)
prenatal specimen must be typed for
ABO and RhD
For tube testing, an antibody-enhancing medium can increase sensitivity of the assay.
polyethylene glycol (PEG)
low ionic strength solution (LISS)
The relative concentration of all antibodies capable of cross- ing the placenta and causing HDFN is determined by
Antibody titration
the recommended test for RhD-positive fathers when the mother has anti-D antibody
zygosity genotype testing
the clinical diagnosis of fetal anemia can be made using an ultrasound technique called
*** The measurement is based on the reduced blood viscosity at lower hematocrits and resulting in faster velocity of the blood.
fetal middle cerebral artery peak systolic velocity (MCA-PSV)
done to determine fetal hematocrit.
Cordocentesis
umbilical vein is visualized at the level of the cord insertion into the placenta
high-resolution ultrasound with color Doppler enhancement of blood flow
monitor amniotic fluid bilirubin levels has been replaced with MCA-PSV
Amniocentesis
amniotic fluid is tested by a spec- trophotometric scan optical density (∆OD) at
450 nm
goal of intrauterine transfusion is to
maintain fetal hemoglobin above 10 g/dL
the infant’s RBCs can be heavily antibody-bound with maternal anti-D, causing a false-negative Rh type, or what has been called
Blocked Rh
most important serologic test for diagnosing HDFN is the
DAT with anti-IgG reagent
collection from the donor are selected to reduce the risk of hyperkalemia
RBCs units less than 7 to 10 days
After a two-volume exchange transfusion
90% of the red blood cells have been replaced
50% of the bilirubin has been removed
used to metabolize the unconjugated bilirubin to isomers that are less lipophilic, less toxic to the brain, and able to be excreted through urine
Phototherapy at 460 to 490 nm
is used to treat hyper- bilirubinemia of the newborn caused by HDFN
Intravenous immune globulin (IVIG)
The first dose of RhIG is provided at
28 weeks of gestation
The second is provided at
After delivery
it is recommended to give RhIG within
72 hours after delivery
a maternal blood smear is treated with acid and then stained with counterstain.
Kleihauer-Betke test
Fetal cells contain ______which is resistant to acid and will remain pink
Hgb F
The most common genetic backgrounds that account for this serologic typing problem are called
weak D phenotypes
