Hemolytic Disease of the Fetus and the Newborn

what is hemolytic disease of the fetus and newborn (HDFN)

a disorder of the fetus or newborn in which fetal RBCs are destroyed by maternal IgG antibodies

define prenatal/antenatal

time period before birth

define antepartum

period between conception and onset of labor in reference to the mother

define neonatal

time period within the first 28 days after birth`

define perinatal

period between 28 weeks gestation and 28 days after delivery

define parity (para)

number of live births

define gravidity (grava)

number of pregnancies

define hydrops fetalis (HDN)

fetal hemolysis occurs as cardiac output increases, leading to cardiac failure and fluid accumulation in the abdomen

the period between 28 weeks gestation and birth is referred to as

perinatal

what is the role of the placenta during pregnancy

the placenta acts as a site of gas, nutrient, and waste exchange between mother and fetus

this immunoglobulin can cross the placenta

IgG

how does ABO HDN happen

naturally occurring anti-ABO IgG crosses the placenta

ex) mom is type O, baby is type A or B

how does Rh HDN occur

during first pregnancy, mother is NOT immunized against the foreign antigens. When she delivers, mom is exposed to fetal antigens causing her to develop IgG antibodies that can target fetal cells in subsequent pregnancies

if a child is Rh negative and mom has anti-D, does HDN occur

no, because child’s RBCs do not have D antigen

list some events and procedures that can cause maternal exposure to fetal antigens

amniocentesis

spontaneous/induced abortions

cordocentesis

ectopic pregnancy

abdominal trauma

ABO HDN can occur when mother is type O and baby is type

A or B

what 3 elements are needed for HDN to occur

1. mother must make an IgG antibody to a foreign RBC

2. the fetus must possess the antigen the IgG antibody targets

3. the antigens must be well-developed at birth

what are the expected lab results for ABO HDN (which pregnancy, clinical findings, serologic results, hematology results, and chemistry results)

• HDN possible in first pregnancy

• clinical findings include mild to moderate jaundice

• ABO & D type: mom is O and baby is A or B; DAT test is neg or weak pos; Antibodies include anti-A, B, or AB

• hematology results show mild anemia, mild increase in reticulocytes, spherocytes, mild increase in nRBCs

• chemistry results show a mild increase in bilirubin 24 - 48 hrs after birth

what are the expected lab results for Rh HDN (which pregnancy, clinical findings, serologic results, hematology results, and chemistry results)

• most frequent after first pregnancy

• clinical findings include mild to severe jaundice & edema

• ABO & D type: mom is D-neg and baby is D-pos; DAT test is pos; Antibodies include anti-D

• hematology results show moderate to severe anemia, great increase in reticulocytes, macrocytes & hypochromia, great increase in nRBCs

• chemistry results show a moderate to severe increase in bilirubin

anemia in Rh HDFN is

moderate to severe

what are some theories as to why ABO HDN is less severe than Rh HDN

1. presence of A or B substances in fetal tissues neutralize maternal antibodies

2. poor development of ABO antigens in prenatal period

3. reduced number of ABO antigens in prenatal period

how does RhIG work

it hasn’t been fully discovered, but a working theory is that specific cytokines work to suppress a primary immune response in the mother to positive fetal RBCs

a recent RhIG theory suggests that specific ____ suppress a primary immune response after RhIG administration

cytokines

list 2 other antibodies commonly implicated in HDN that are not anti-ABO or Anti-D

anti-c and anti-K

***Rhogam won’t work for these because it only works for anti-D

which of the following antibodies has NOT been implicated in HDFN?

• anti-c

• anti-Fy^a

• anti-K

• anti-Le^a

anti-Le^a

what is some common lab testing done for the initial prenatal visit

ABO/D typing

antibody screen for IgG antibodies (if screen is positive, then ID antibody and perform titer)

what is some common testing performed during the follow-up visits if IgG antibody was identified

selected reagent cell panel should be run to exclude other clinically significant antibodies

an antibody titer should be performed every 4 weeks

what are some common tests performed at 26-28 weeks gestation

confirm D-type

repeat antibody screen

what 2 test results are red flags for MLS during prenatal period

antibody titer > 32 or a 2 dilution increase in titer

for Rh neg mothers at 26-28 wk gestation, which tests are performed prior to RhIG therapt

Rh and Antibody screen

what tests are used to screen for fetal distress

1. amniocentesis - measure bilirubin levels & use a Liley graph or Queenan graph to determine course of action

2. doppler flow studies - measure peak velocity of blood flow in middle cerebral artery (MCA) to measure degree of fetal anemia

3. percutaneous umbilical blood sampling (PUBS) or cordocentesis - a needle is inserted into an umbilical cord vessel close to the placenta and a hematocrit, DAT, and blood type is performed

indirect bilirubin has a spectral peak at ___ nm

450

which of the following is a non-invasive test used to screen for fetal distress?

• doppler flow studies

• amniocentesis

• PUBS

• choronic villus sampling

doppler flow studies

what testing is done on maternal blood and why

• ABO/D type = to determine if RhIG is needed

• Antibody screen/Antibody ID = if transfusion is needed or HDN suspected

• fetal screen (Rosette)/Kleihauer-Betke = making sure fetal screen is a true positive

what testing is done on fetal blood and why

• ABO/D typing = if RhIG is needed & weak D testing required

• DAT = test for HDN and/or blocking phenomenon

• elution = removed antibody from DAT positive cells to test specificity

what test is NOT performed on cord blood (or infants) after birth

Antibody screen

what is the blocked D phenomenon

maternal anti-D coats the red cells of baby, causing baby to type as Rh negative. This causes a positive IgG DAT, because the maternal anti-D blocks reagent IgM anti-D from agglutinating cells. Thus, a false negative Rh test occurs.

1 dose of RhIG covers ___mL of D-positive blood

30

using the Rosette test, <1 rosette perf 3 lpf means

give 1 dose of RhIG

RhIG is given to mothers who are _____ with ____ infants

neg; pos

compatibility for an exchange transfusion is tested by crossmatching

donor cells and maternal serum