Path 2 Ex 3

Front 1

• A pathologic condition that results in accelerated destruction of red blood cells in the fetus and newborn.

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Hemolytic Disease of the Newborn

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what is Hemolytic Disease of the Newborn (HDN) associated with

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RBC abnormalities (membrane defects, enzymopathies) and acquired disorders (infections, alloimmunization to RBC antigens)

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The most common form of HDN is

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alloimmunization to RBC antigens-(Focus on immune mediated)

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Immune HDN occurs when

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Maternal immunization vs paternal antigens on RBC
Ex: Mom is Rh(D) negative
Dad is Rh(D) positive
Fetus is Rh(D) positive, and Mom is exposed to fetal cells, stimulating her to make anti-Rh(D)

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does immune HDN affect first pregnancy?

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No, because the first pregnancy serves as : stimulus for immunization (RBC from fetus) and is often not affected; subsequent pregnancies would then be potentially be affected

Front 6

HDN effect is via which antibody and why?

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limited to IgG antibodies

Antibody must be able to cross placental barrier to cause injury to fetal rbc
Transported by one way active transport by interaction between immunoglobulin and synciotrophoblast (placenta) Fc receptors

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fetus with anasarca ( accumulation of serous fluid in various tissues and cavities of the body), ascites, and heart failure in association with anemia, hypoxia and low serum protein due to liver failure, often resulting in death in utero

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Hydrops fetalis (aka erythroblastosis fetalis)

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What causes hydrops fettles?

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hypoxic effects of anemia and toxic effects of metabolites from hemoglobin degradation
Principal adaptive response to fetal anemia is expansion of fetal erythropoiesis, which leads to hydrops

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clinical syndrome caused by indirect bilirubin (unconjugated) accumulation in the central nervous system.

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Kernicterus

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Kernicterus manifestations

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nerve deafness, severe brain damage, mental retardation, spasticity, athetoid movements, death

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Anti-D Immune Globulin Prophylaxis is given when

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Rh negative pregnancy with likely Rh positive fetus who has NOT already made anti-D:
give at 28 weeks and
within 72 hours postpartum (and after invasive procedure or trauma)

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Prevention of immunization with IV Rh(D) immune globulin is also important after transfusion (platelets) in women of

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childbearing age (usu less than 50 y.o.)—give within 72 hours of exposure

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administration of Rh immune globulin (RhIg) failures (residual risk) likely due to

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Small fetal-maternal hemorrhage (FMH) occurring prior to RhIg administration at 28 weeks
92% of women who develop anti-D during pregnancy do so at or after 28 weeks gestation
Large FMH occurring between 30-38 week gestation

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The clinical management for a • Maternal antibody screen (for antibodies to D and other significant RBC antigens) on Rh(D) negative women with uncomplicated pregnancy:

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– First prenatal visit (also sample from Dad for ABO and Rh typing)
– 28 weeks gestation
– At delivery
– Alloimmunization to other RBC antigens (c,C,e,E,K1, Fy, Jk, etc) managed in similar manner to Rh(D) alloimmunization BUT there is little data to confirm this is correct approach

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What does a A Positive Antibody screen mean

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the fetus is at risk for developing HDN and the following may be required:

Maternal antibody titer
Paternal zygosity
Ultrasound/Middle Cerebral Artery Doppler
Amniocentesis

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Maternal Antibody Titer are determined by the

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dilution of serum where RBC agglutination no longer occurs; determination of severity

Critical titer: varies from 8 to 32, but most institutions use 16 (1:16)

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How is the antibody titer measured in a pregnancy?

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In the first affected pregnancy, serial antibody titers are determined every two to four weeks after 20 weeks of gestation as long as the titer remains below the critical titer.

Front 18

If there is paternal heterozygosity for the antigen of interest what can be done?

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amniocentesis can be done to obtain fetal cells for genotyping. Amniocentesis should also be performed when the critical titer is reached or if there has been a previous seriously affected fetus or infant

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this method has emerged as the most accurate tool for predicting fetal anemia in at-risk pregnancies

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Doppler assessment of the fetal middle cerebral artery (MCA) peak velocity . The anemic fetus preserves oxygen delivery to the brain by increasing cerebral flow

Front 20

Amniocentesis if done improperly can cause a rise in maternal antibody titer how?

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transplacental passage of the needle because this can lead to fetomaternal hemorrhage

Front 21

Fetal hemolysis can be determined by

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Bilirubin present in amniotic fluid. Bilirubin is detected by Liley curve (optical density of amniotic fluid at 450 nm on the spectral absorption curve (delta OD450) i)

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What is Intrauterine Transfusion

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Antigen negative (D negative or other implicated antigen) RBC transfused via umbilical vein (IVT or intravascular transfusion).
Repeat procedures often required to prolong pregnancy until gestational age with better chance of survival is reached (34 weeks)

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Milder forms of HDN can be treated by

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Phototherapy. UV exposure increases bilirubin catabolism by producing excretable water-soluble bilirubin metabolites

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What can be done when phototherapy fails?

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Use Exchange Transfusion, In newborn, catheter inserted through umbilical vein

Removes incompatible RBC, reduces bilirubin

Slowly, over 60-90 minutes, 5-10 mL of blood are exchanged by initially removing newborn blood and replacing equal volume with donor blood ( RBC reconstituted with group AB plasma)

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All Rh(D) negative postpartum patients should have antibody screen and screen for feto-maternal hemorrhage (FMH) to determine need for anti-D prophylaxis
This can be done by

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Rosette test
Kleihauer-Betke acid elution test

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Rosette test

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: detects small numbers of Rh(D) positive cells in a Rh(D) negative suspension. Detects FMH of about 10mL.

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Kleihauer-Betke acid elution test

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determines percentage of fetal cells which can then be used to calculate volume of feto-maternal hemorrhage

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what should be done If antibody screen is negative, and rosette test is negative

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, one vial (300 ug) Rh immune globulin given

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what is ABO HDN

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Usually seen with a Group O mother of a Group A or B infant
Proportion of anti-A or B made by Group O is not just IgM but IgG, which can cross the placenta
Generally mild disease but may need exchange transfusion after birth

Front 30

what is Anti-Kell HDN

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Antibodies to Kell (K1) antigen

Anti-Kell most common antibody outside of Rh(D) in pregnant women
Kell antigen expressed on progenitor cells

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what can anti-kell HDN cause?

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Can have severe disease
No correlation with titer
No association with increased bilirubin in amniotic fluid –use fetal blood sampling to get hematocrit