Alloimmunization Flashcards
immune response to foreign antigen after exposure to different cells or tissues
alloimmunization
How can alloimmunization affect the fetus?
transplacental passage → hemolytic disease
most common 3 red blood cell alloimmunization that account for majority of fetuses with severe disease that require intrauterine transfusion for fetal anemia or cause hydropic still birth
anti D
anti c
anti Kell
what are two common factors of alloimmunization?
ABO compatibility and status of father
Rh D alloimmunization can be caused by a fetus with _____ and a mother with _____
Rh + erythrocytes
Rh - erythrocytes
in order for Rh D alloimmunization to occur a significant number of fetal erythrocytes must gain access to maternal circulation, how can this occur?
ectopic pregnancy surgery miscarriage D&C C-section delivery fetal maternal hemorrhage (placenta previa or abruption placentae)
What procedure increases the risk of maternal fetal hemorrhage? What should Rh-D negative mom get prior to procedure?
chorionic villus sampling
RhoGAM
what 3 conditions can result in Rh D alloimmunization?
- Rh (+) fetus in Rh (-) mom
- mom must have immunogenic capacity to produce antibodies against Rh D antigen
- significant number of fetal erythrocytes must gain access to maternal circulation
If breach of choriodecidual space is suspected, how soon should you administer RhoGAM?
within 72 hours
in subsequent pregnancies if a mother carries Rh (+) fetus, what affect can the anti Rh antibodies have on the fetus?
hemolytic anemia jaundice kernicterus hepatosplenomegally fetal hydrops
condition characterized by abnormal collection of fluid in the fetus
hydrops fetalis
at least 2 of the following are places were fluid abnormally collects and results in hydrops fetalis
edema (>5 mm)
ascites
pleural effusion
pericardial effusion
two classifications of hydrops fetalis
immune and nonimmune
what two things are hydrops fetalis frequently associated with?
polyhydramnios and thickened placenta (>6 cm)
common complaints of hydrops fetalis
polyhydramnios in thick placenta size is greater than dates fetal tachycardia (>160) decreased fetal movement abnormal serum screening antenatal hemorrhage
maternal antibodies against RBC of fetus cross the placenta and coat fetal RBC and destroy them
immune hydrops
severe anemia as a result of immune hydrops leads to….
high output CHF
liver and spleen increases RBC production → hepatic circulatory obstruction (Portal HTN)
hemolytic disease of newborn
any cause of hydrops fetalis that is not immune related → failure of interstitial fluid to return to the venous system
nonimmune hydrops
what are some causes of nonimmune hydrops?
cardiac failure
impaired venous retun
obstruction of normal lymphatic flow
increased capillary permeability
method used to screen for antibodies for anti D and other atypicals
indirect Coombs test
Indirect Coombs test indicates Rh (-) woman is alloimmunized to Rh D, what is the next step?
order anti-D titer → roughly correlates with disease severity
Doppler flow studies
Anti-D titer of ___ requires further assessment
1:16
If a titer is less than 1:16, how often should you follow them with titer?
monthly
preferred method and standard of care for monitoring fetal anemia
Doppler velocimetry of middle cerebral artery
