Haemolytic Disease of the Newborn/Foetus Flashcards
What is HDNB
Life span of foetal RBCs shortened by mother’s antibodies - given via placental transfer - occurs intrauterine and can cause death in utero
What does the disease involve?
Maternal alloimunisation, transplacental transfer of IgG antibodies to foetus, destruction of foetal RBCs, Most commonly caused by the RhD antigen
What has lead to a decrease in cases and deaths of HDNB?
1950s - MOA understood - RBCs attacked by mother’s antibodies due to mother & foetus having incompatible blood types
1970s - antenatal screening introduced - preventative treatment given
What passes from mother to foetus usually to protect the foetus?
Antibodies - babies have primitive immune system - mother’s antibodies pass through placenta - ensures survival until immune system develops
What antigen-antibody reactions cause HDNB?
-Usually RhD antigen
-Also from Rh C,c,E, & e antigens
Why isn’t HDNB usually caused by the ABO system?
Foetal RBCs have less ABO antigens and ABO antibodies tend to be IgM
What type of antibodies usually cause HDNB?
IgG
What type of pregnancies are at risk of HDNB?
RhD- mother carrying RhD+ baby (RhD antigen acquired from father)
What pregnancies are more at risk of HDNB?
The 2nd pregnancy where mother is RhD- and foetus is RhD+
How is the mother usually sensitised to the foetal RBCs?
During birth, falls during pregnancy, bleeds - some foetal blood enters the mother’s blood - mother produces anti-D (IgM) as an immune response - won’t cross placenta - upon 2nd exposure the mother will produce IgG - will cross placenta and bind with the RhD on foetal RBCs
Describe mild HDNB
Small rate of haemolysis tolerated - cause mild anaemia & jaundice
Describe severe HDNB
Bilirubin removed from foetus during pregnancy via placenta - Neonate’s immature liver can’t metabolise increased rate of bilirubin - accumulation of bilirubin in blood - may enter the brain & cause kernicterus (permanent neurological damage/death)
Complications of HDNB
Anaemia, jaundice (increased bilirubin in neonate), kernicterus (yellow staining of brain - excessive bilirubin enters brain - damages brain), hydropic (bloated with fluid), hydrops foetalis (water foetus - bloated with oedema), erythroblastosis foetalis (large number of NRBCs in foetal peripheral blood)
What is now given to all RhD- mother’s carrying RhD+ babies?
Anti-D Ig injections at
~28 weeks (when RhD antigen starts to develop)
~34 weeks (risk of faeto-maternal haemorrhages)
~Postpartum (not needed if there is a negative Kleihauer test)
~antepartum bleeds or preeclampsia (risk of sensitisation)
What are mothers tested for to avoid HDNB?
History (previous transfusion, past pregnancies, history of children with HDNB)
ABO & RhD group determined at least 2 times - identify RhD- mothers
Antibody screen (mother’s plasma) using IAT to detect antibodies - further testing to determine what type of antibody is present (clinical significance)
