Hemolytic disease of the Fetus & Newborn

Question 1

Hemolytic disease of the fetus

Answer 1

premature RBC destruction results in disease varying from mild anemia to death in utero
(bilirubin is processed by mama liver)
worry about anemia

Question 2

hemolytic disease of the newborn

Answer 2

RBC destruction results in anemia & elevated levels of bilirubin in new born

Question 3

the placenta

Answer 3

exchange site for oxygen, nutrients, & waste
barrier between mother & baby circulations & reduces exposure to foreign antigens
prevents fetal cells from entering mom’s circulation

Question 4

when does sensitization of the mother occur?

Answer 4

anytime fetal RBCs enter mother’s circulation:
delivery, amniocentesis, chorionic villi sampling, spontaneous/induced abortion
ectopic pregnancy
abdominal trauma

Question 5

requirements for HDFN to occur

Answer 5

mother must have developed antibody
fetus must posses the antigen
antigen must be well developed at birth

Question 6

greatest threat of hemolytic disease of the fetus

Answer 6

cardiac failure due to uncompensated anemia

Question 7

greatest threat of hemolytic disease of the newborn

Answer 7

premature baby liver that does not produced glucuronyl transferase to conjugate indirect bilirubin & can cross blood-brain barrier to bind to CNS tissues = kernicterus, deafness, mental retardation or death

Question 8

3 classes of HDFN

Answer 8

1. RhD
2. ABO
3. non-anti-D alloantibody-mediated

Question 9

RhD HDFN

Answer 9

anti-D responsible for most severe cases of HDFN

anti-D #1 cause of death in HDFN

Question 10

ABO HDFN

Answer 10

most common HDFN
most cases are subclinical & do not need treatment
A/B substances in fetal tissues & secretions neutralize most maternal antibodies
large portion of anti-A/B are IgM; IgG are low titer

Question 11

group A baby & group O mommy

Answer 11

ABO HDFN
group O make an anti-A,B antibody that is IgG
can affect first pregnancy

Question 12

cutoff for hyperbilirubinemia in infants

Answer 12

> 5 mg/dL

Question 13

second most common cause of HDFN

Answer 13

anti-c antibody & can be in combination with anti-D

Question 14

3rd most common cause of HDFN

Answer 14

anti-K

Question 15

Kell HDFN

Answer 15

kell is expressed on RBC precursors!!!!

HDN is MUCH more severe when due to kell antibodies bc they target precursors & lead to SEVERE anemia

Question 16

prenatal work up

Answer 16

D neg mothers need to be IDed
mothers with IgG antibodies capable of causing HDFN need to be IDed
no testing for ABO HDFN
& antibody titration if necessary

Question 17

antibody titration

Answer 17

predict HDFN; titer done early in pregnancy & repeated every 4-6 weeks & specimen is frozen
two-dilution rise in titer is an indication for further monitoring

Question 18

critical titer of antibody?

Answer 18

> 16

this is high enough to affect the fetus

Question 19

Doppler ultrasonography

Answer 19

measures blood velocity
rate is inversely proportional to hgb (faster during anemia)
lower resistance when there are fewer cells

Question 20

postnatal work up

Answer 20

1. mother is Rh neg- need to know about Rhogam doses

2. when HDFN is suspected

Question 21

postnatal mother tests

Answer 21

type & screen
if RhD pos - done
if RhD neg test baby

Question 22

postnatal baby tests

Answer 22

type & screen
if child is RhD neg-> weak D test
if child is RhD neg & mother has anti-D-> perform elution
if child is RhD pos & mother has no anti-D then test for fetal maternal hemorrhage

Question 23

Fetal maternal hemorrhage screen

Answer 23

determine if >20ml of RhD pos fetal blood is in RhD neg mother
neg result: 1 unit of rhogam
pos result: multiple units of rhogam

Question 24

Kleihauer-Betke test

Answer 24

quantifies all fetal cells in mother’s circulation
acid elution of peripheral blood smear
Hgb F is acid stable
hgb A is acid soluble

Question 25

gold standard assay for fetal maternal hemorrhage

Answer 25

flow cytometry!!

immunophenotype RBCs

Question 26

testing on infants with suspected HDN

Answer 26

ABO/D only forward type
antibody screen
DAT - if positive then elution

Question 27

importance of DAT

Answer 27

if infant RBCs are DAT positive, then the antibody MUST have come from the mother
only need IgG not polyspecific

Question 28

RhIG

Answer 28

concentrate of anti-D IgG prepared from pools of human plasma (sensitized to D antigen on RBCs during their lives)
prevent sensitization

Question 29

prevention of RhD HDFN

Answer 29

after RhD neg woman gives birth to a RhD pos child she must receive at least one dose of RhIG

Question 30

one dose of RhIG covers how many ml of whole blood & how many mls of packed blood

Answer 30

30 mL whole blood

15 ml of fetal RBCs

Question 31

1st dose of RhIG at how many weeks?

Answer 31

28 weeks

Question 32

ATDP

Answer 32

anti-D passive

anti-D antibody will show up in women who have recently been given RhIG (only in gel/capture methods)

Question 33

Cordocentesis

Answer 33

transfusion into the umbilical vein
group O, RhD neg
crossmatch compatible with maternal serum
CMV negative
hemoglobin S negative
irradiated
<7 days old blood

Question 34

sunlight

Answer 34

treatment for mild hyperbilirubinemia
photo-oxidizes bilirubin
excreted in urine

Question 35

bili-bed

Answer 35

treatment for moderate hyperbilirubinemia
exposure to blue light
photoisomerizes bilirubin so it can be excreted w/o conjugation in the liver
excreted in the bile

Question 36

exchange transfusion

Answer 36

remove a volume of whole blood from baby & add in the same volume of PRBCs
treat severe bilirubinemia
removes some bilirubin & antibody
removes sensitized RBCs

Question 37

bilirubin & child weight

Answer 37

bilirubin is more toxic the smaller the child

Question 38

ABO HDFN

Answer 38

most common HDFN
most cases are subclinical & do not need treatment
A/B substances in fetal tissues & secretions neutralize most maternal antibodies
large portion of anti-A/B are IgM; IgG are low titer