HDFN Flashcards
HDFN
destruction of RBC’s of the fetus or neonate by maternal antibodies
IgG can cross the placenta by
active transport
most dangerous IgG
IgG1 and IgG3
2 most common types of HDFN caused by
Rh antibodies and ABO antibodies
as little as _____ of fetal RBCs are enough to stimulate formation of Anti- D
1 mL
most antigenic antigen in Rh system
D
does the titer matter when to comes to Kell
no any titer is dangerous
HDFN antibodies almost never a risk
Anti- Lea
Anti- P1
Anti- I
Anti- U
how to limit sensitization to D antigen
give D - blood to D- women
antigen matching aside from D has proven ineffective at preventing severe HDFN why?
pregnancy is much more common than transfusion
IgG causes hemolysis of fetal RBC’s and what destroys IgG tagged cells
Fetal reticuloendothelial system
when the fetus becomes anemic the marrow compensates and this can lead to
erythroblastosis fetalis
-erythroblasts in fetal circulation (young nucleated red cells)
when fetus is anemic is anemic what organs affected
spleen and liver enlarged
hydrops fetalis
used to be fatal, now not
caused by anemia and hypoproteinemia
when rbc are lysed the Hgb released is metabolized to
indirect (unconjugated) bilirubin
BILIRUBIn does not cause a problem for the fetus because it crossed placenta and mother clears it
Anti-D half life
25 days
so RBC destruction still happens after birth
can neonates effectively conjugate bili
no they can’t because they can not excrete it = janudice
toxic amount of bili in baby
18-20
normal = 1
bili buildup in baby called
kernicterus
include= seizures, poor feeding, visual damage, cerebral palsy
prenatal testing for mother
type and screen- 1st tri
if mom is D- and screen is neg= she can get RhIG
if prenatal screen is positive tech must
Antibody ID
if anti-D present find out if true immune or given rhogam
(passive is if previously had Rhogam)
if a mother has true immune anti-D, paternal testing is ordered. baby has to be Rh - if father is
homozygous for antigen
baby may be Rh- if father is
heterozygous
-testing can be done to see if baby inherited antigen
(amniotic fluid)
what test can be done to determine if baby is Rh -
Cell free fatal DNA testing
PCR run on mom plasma which contains fetal DNA detectable at 7 weeks
what is amniocentesis
extraction of portion of amniotic fluid and can measure extent of HDFN, see specific antigen, access lung maturity
what can cause FMH
amniocentesis
risk of sensitizing mother to fetal antigen if a bleed is causes
when is amniocentesis done
27-40 weeks
if true immune anti-D physician may order
titration
FMH and follow up only performed on D-negative patients
fetomaternal hemorrhage screen
has fetal blood crossed maternal circulation
Kleihauer-Betke
ordered if FMH screen is positive
determines how much fetal blood in maternal circulation
what happens in antibody titration
2 fold serial dilution of maternal plasma
-tests against RBCs that are homozygous for the specific antigen
IAT
express titer as reciprocal of highest dilution
only run on specific antibody!!
agglutination scores
4+ = 12
3+ = 10
2+ = 8
1+ = 5
if titer increases during pregnancy
fetus should be presumed to be antigen +
(mom’s immune system having secondary response)
consider intrauterine exchange
RhIG titer should never be over
4
if titer >8 a second titer needs to be done at
18-20 weeks
run in parallel with previous titer
if titer greater than 16
fetus will need middle cerebral artery peak systolic velocity
if titer is 16 or less it needs to be measured every
2-4 weeks from 2nd tri on
if titer consistently less than 16
lower risk except for KELL
(titer doesn’t determine severity for KELL)
Anti-D binds
D-positive fetal cells and removed from circulation
do not sensitize the mother to D antigen
indications for RhIG
Rh - patient
10-28 weeks gestation if type and screen negative
within 72 hours of birth
abdominal trauma
amniocentesis
spontaneous/ induced abortion
one dose of RhIG removes
30 mL of fetal blood in circulation
post partum testing cord blood
group O and Rh- mothers need newborn’s type determind
Rh - mothers with Rh + baby with negative screen / passive anti-D mom will get 1 dose of RhIG
after mother gets another dose of RhIG after birth they need
fetomaternal hemorrhage screen
negative- no more RhIG
Positive quantify blood
if FMH is +
blood be quantified to determine additional RhIG needed
RhIG dose calculation
Doses = Volume FMH/30 +1
volume of FMH =
%fetal cells in maternal circulation x 5000 mL
specimen for testing for newborns
cord blood is typical specimen- heelstick if necessary
ABO/Rh on newborns
forward typing
no back type or else mothers cause no antibodies
may see weaker reactions
weak D done on all D- infants
why weak D testing on infant
mother could still make antibodies to D antigen from baby
DAT newborns
washing important
looking got IgG
Rh antibodies aren’t effective at fixing complement
newborns elution
if DAT is positive
-antibody from mom
if mom type and screen negative - could be antibody to uncommon blood group
if newborn DAT positive what is monitored
serum bili
CBC show evidence of anemia
spherocytes
nRBCs
polychromasia
most common cause of HDFN
ABO since RhIG happened
usually anti-A,B
naturally occuring
small amount of anti-A and anti-B are
IgG
these can cross the placenta and hemolyze fetal cells
testing for newborns
front type fetal cells ABO, DAT, elute antibody and ID antibody
who are protected from sensitization from D antigen
mothers incompatible with fetal RBC’s for both ABO and D
ABO incompatible cells are destroyed in maternal circulation before anti-D can be formed
treatment of HDFN
intrauterine transfusion
exchange transfusion
induction
phototherapy
normal Hgb for newborn
14-20
intrauterine transfusion
inject pedi-pak directly into umbilical vein
goal: maintain Hgb > 10
may need to repeat every 2-4 weeks until delivery
indications for intrauterine transfusion
Middle cerebral artery-peak systolic velocity suggest anemia
cordocentesis < Hgb 10
amniocentesis elevated bili
hydrops fetalis
exchange transfusion
replace newborn’s circulation blood
pre and postpartum
goal: improve Hgb level to treat anemia, reduce hemolysis to prevent bili
who is most likely to need an exchange transfusion
premature neonates
liver and kidneys less developed than full term
removes antigen + cells, bili
AABB recommends giving
ABO matched units
zone 1 liley graph
low risk
liley graph zone 2
moderate
liley graph zone 3
high risk need intervention
more bili= more dangerous
liley graph detects
amount of bili present in amniotic fluid
induction
possible option if fetus is in high risk group of Liley graph at 32 weeks or later
lecithin/sphingomyelin ration over
2:1 indicates sufficient lung maturity
what may require exchange transfusion after birth
induction
better to deliver and than transfuse
what light is best for phototherapy
490 nm
cuts bili half life by 50%
how does phototherapy work
light isomerizes unconjugated bili and makes it water soluble and can be excreted by neonate
