Red Blood Cell Isoimmunization Flashcards
Whats the pathophysiology behind it?
Blood groups
Blood classified -ABO and rhesus genotype.
Rhesus genotype- 3 linked gene pairs. One allele is dominant ro the other: C/c, D/d, E/e. 1 allele from each parent in mendellian fashion.
Isoimmunization- D gene-
Dominant: DD, Dd express D antigen and are D rhesus +ve.
Homozygous recessive: dd : D rhesus -ve.
Immune system also recognises it as foreign.
How is sensitization happening?
Small # of fetal blood crosses placenta esp during delivery.
If babes- D rhesus +ve and mum D rhesus -ve- mother will mount an immune response( sensitisation) creating anti-D Abs.
Whats haemolysis/ rhesus haemolytic disease?
Immunity = permanent
If mother exposed to antigen again - subsequent pregnancy- ⬆️⬆️ Abs are rapidly created. Cross, bind to fetal blood cells- destroed in fetal reticuloendothelial system.
This can cause hawmolytic anaemia–> death
What similarly happens after blood transfusions?
Anti-c & anti-Kell( non-rhesus Ab) after transfusions.
What are some potentially sensitizing and events?
- Termination of pregnancy
- ERPC- evacuation of retained products of conception after miscarriage
- Ectopic pregnancy
- Vaginal bleeding
Whats red blood cell isoimmunization?
Occurs when the mother mounts an immune response against antigens on fetal red cells that enter her circulation.
Resulting Abs cross the plaventa and cause fetal red cell destruction.
How would you prevent a rhesus sensitisation?
- production of maternal anti-D prevented by administration of exogenous anti-D . Any fetal Red cells that crossed- binds to their antigens and prevents recognition by maternal Abs.
Anti-D given even if both parents rhesus -ve - cz possible non-paternity- care needed !
Anti-D is pointless if maternal anti-D present cz sensitization has occured.
In what other situations are Anti-D given? Antenatally?
- Antenatal: At 28weeks- anti-D (1500IU) given to ALL rhesus -ve women.
- 72hrs after sensitization event-benefit- within 10 days
A. Miscarriage
B. Threatened miscarriage after 12 weeks
Or before if uterus intstrumented- ERPC
C. E topic pregnancy
D.termination of pregnancy - After in utero procedures like amniocentesis and after
4.external cephalic version - Fetal death
- Antepartum haemorrhage.
Postnatally?
Neonates blood group checked and if rhesus +ve Anti-D given to mum within 72hrs of delivery.
Kleihauer test also performed- asses fetal cells in maternal circulation- 2rs of birth to detect larger fetomateenal haemorrhages- require larger doses of Anti-D.
When is the anti-D unnecessary?
If Neonate is rhesus -ve
How do we prevent the rhesus disease?
At 28 weeks check all women for Abs
Rhesus -ve women- given Anti-D at 28weeks, after bleeding or potentially sensitizing evet and after delivery if neonate us rhesus positive.
How often do we see the rhesus disease?
15% caucasian, fewer african and asian are rhesus -ve.
Anti-D- perinatal deaths
Anti-c, anti-E and anti-Kell- fetal anemia and post-natal jaundice.
What are some manifestations of the rhesus disease?
Abs will cross the placenta and cause haemolysis.
Mild-Neonatal jaundice -
If more- neonatal anaemia.- haemolytic
Severe- in utero anemia–> cardiac F, ascites, oedema (hydrops) —> fetal death.
How does rhesus disease worsens? .
With successive pregnancies as maternal Abs production increases
How do you identify isoimmunization?
Unsenitised women- screend at 28 weeks gestation.
Maternal Blood sampling for fetal cells- test for fetal rhesus- when father heterozygote.
Amniocentesis, but also has risks.
If anti-D levels are 10- investigate.
USS.
