HDFN Flashcards
term used to describe the condition in which maternal antibody is reacting with antigens on the baby’s rbcs
hemolytic disease of the fetus and newborn
pathophysiology of HDFN
maternal antibody crosses placental barrier to fetal circulation, attaches to corresponding antigens on baby’s RBCs, and antibody-coated cells are destroyed by macrophages in fetal spleen
HDFN maternal antibodies are what antibody class
IgG
placental transfer factor found on what antibody class?
IgG
pathophysiology behind name erythroblastosis fetalis
fetal marrow responds to moderate or severe disease by increasing red cell production (ERYTHROPOIESIS) and releases red cells into circulation before they mature resulting in nucleated red cells (ERYTHROBLASTS)
IgG subclasses more efficient at causing hemolysis
IgG1 and IgG3
which IgG subclass is associated with more severe HDFN?
IgG1
most common cause of ABO HDFN
anti-A,B from O mother
offending antibody in Rho HDFN
anti-Rho(D) or its combinations, anti-rh’(CD) and anti-rh’‘(DE)
most common reason for positive DAT in cord blood testing
ABO antibodies
jaundice in ABO HDFN
not present at birth, appears 6-24 hours after birth, resolved by bili lights
expected findings in ABO HDFN
mild jaundice 24 hours after birth spherocytosis polychromasia nRBCs ABO incompatibility between mother and child maternal Ab screen negative cord DAT weakly positive or negative presence of IgG anti-A, anti-B, or anti-A,B in cord plasma and eluate
can ABO HDFN occur in first pregnancy?
yes
can Rho HDFN occur in first pregnancy?
not expected
amount of D positive fetal blood needed to immunize D negative mother
0.1 mL
___ HDFN protects the fetus against ___ HDFN
ABO - Rh
ABO incompatible fetal cells will be rapidly removed from maternal circulation by anti-A or anti-B before anti-D can be produced
most common “other” HDFN
anti-K
anti-c
anti-E
what makes anti-K HDFN the most clinically significant “other” HDFN?
suppresses fetal erythropoiesis, which exacerbates fetal anemia
effects of HDFN in utero
anemia
increased hematopoiesis
hepatosplenomegaly
hydrops fetalis
what causes hepatosplenomegaly in HDFN?
liver and spleen enlarge due to increased RBC production, spleen removes baby’s antibody coated cells
what form of bilirubin is increased in HDFN?
indirect
how is indirect bilirubin cleared in utero in HDFN?
passes back into maternal circulation, conjugated by mother’s liver, excreted
hydrops fetalis
generalized edema
effusions
portal hypertension
cardiac failure
what causes kernicterus in HDFN?
unconjugated bilirubin builds up in infant because liver cannot process into direct bili and clear product (maternal liver no longer clearing after birth)
excess bili is toxic to brain tissues, leads to irreversibly damage to CNS and mental retardation
effects of HDFN after birth
continued risk of hydrops fetalis/anemia
jaundice 6 hrs after delivery
kernicterus
why are premature infants more likely to be affected by kernicterus than full-term infants?
immaturity of blood-brain barrier
specific transferase that breaks down indirect bili to direct bili
uridine diphosphoglucuronyl transferase
half-life of IgG antibody
25 days
physiologic causes of neonatal jaundice other than HDFN
hyperbilirubinemia of premature infants
hereditary spherocytosis
congenital hemolytic anemia
metabolic causes of neonatal jaundice
maternal diabetes
galactosemia
G6PD deficiency
pyruvate kinase deficiency
infection causes of neonatal jaundice
congenital syphilis
hepatitis
rubella
CMV
drug cause of neonatal jaundice
overdose of vitamin K
prenatal testing to diagnose HDFN
identify at-risk women serologic testing on mom antigen type dad ultrasounds to monitor amniocentesis cordocentesis
semi-quantitative means of measuring the amount of antibody
antibody titration
prozone phenomenon in first titer tube due to?
excess antibody to antigen ratio
clinically significant antibody titer
initial 32
change of 2 tubes or more
PUBS
percutaneous umbilical sampling of baby’s blood
PUBS usually done when:
mother has history of HDN in her kids
Ab titer is 32 or higher
significant change in titer
PUBS can be performed as early as ___ weeks gestation
16
fluid drawn from amniotic sac about 26 weeks of pregnancy
amniocentesis
amniocentesis results plotted on _____
Liley Graph
analysis of amniotic fluid:
color turbidity contamination with blood pH dilution L/S ratio
antigen typing of father: homozygous
fetus is at risk of HDFN
antigen typing of father: heterozygous
fetus may be at risk of HDFN. genotype of fetus can be determined by PCR
what does fetal blood flow in brain show in HDFN?
increased flow = anemia in fetus. faster blood flows is greater degree of anemia
why may red cells from babies with Rho-HDN appear Rn negative at immediate spin?
D antigen site covered with mother’s anti-D
weak D test result if baby has positive DAT
invalid
most important diagnostic test for HDN
Direct Coombs
lab testing on cord blood samples
Abo and Rh (Weak D on IS negative to Rh negative mom)
what is done if cord blood DAT is positive?
elution and ID of antibody
bilirubin testing
why is cord blood testing done on babies from type O mothers?
assess risk of ABO HDN due to anti-A,B
why is cord blood testing done on babies from Rh negative moms?
to determine need for RhIg
other testing ordered on some cord blood samples
RPR
agar gal on black and asian babies
prenatal management and treatment of ABO HDN
not routinely done
postnatal treatment of ABO HDN
phototherapy
exchange transfusion in severe cases
why is ABO HDN not routinely treated with prenatal management?
anti-A, anti-B titers don’t correlate to disease severity
risks of fetal monitoring and fetal trx are greater than risk of ABO HDFN
ABO HDN occurrence in first born
40-50%
Rh HDN occurrence in first born
5%
DAT in Rh HDN
positive
DAT in ABO HDN
positive or negative
which HDN are spherocytes present?
ABO
which HDN frequently requires exchange transfusion?
Rh
treatment of severe HDFN
intrauterine transfusion
early induction of labor
exchange transfusion after birth
human serum albumin
purpose of human serum albumin transfusion for HDFN
binds unconjugated bilirubin, preventing deposition in fat-rich brain cells
risk of human serum albumin transfusion for HDFN
can aggravate congestive heart failure
2 routes of transfusion for intrauterine transfusion
intraperitoneal
intravascular
intrauterine transfusion route where needle is inserted across maternal abdominal wall and uterine wall into fetal peritoneal cavity and catheter is threaded into peritoneal cavity of the fetus
intraperitoneal route
intrauterine transfusion route where fetal circulation is accessed through placental cord
intravascular route
IUT route that requires several days for absorption into vascular space
intraperitoneal
where are RBCs absorbed in fetus in intraperitoneal route?
subdiaphragmatic lymphatics
risks of IUT
perforation of internal structures bleeding from cord puncture site infection fetal bradycardia premature labor premature leakage of amniotic fluid
why does jaundice not occur before delivery?
bilirubin produced by breakdown of cells in fetal spleen passes via placenta to maternal circulation and excreted by liver
purpose of exchange transfusion
remove sensitized cells from baby’s circulation
introduce antibody-free cells with oxygen carrying capacity
reduction of plasma bilirubin to prevent kernicterus
reduction of circulating maternal antibody
restore normal cardiac function
blood requirements for intrauterine or exchange transfusion
irradiated CMV reduced risk hemoglobin S negative lack corresponding antigen less than 7 days old preferred
what may be used for red cells in exchange transfusion if it is difficult to find antigen negative blood due to high antigen frequency or multiple antibodies?
mother’s washed red cells
