Rhesus Incompatibility Flashcards
does mum and baby’s blood mix?
The mum and babies blood does not mix, but becomes in close contact at the placental membrane.
what does it mean if someone is rhesus pos?
- If someone is rhesus positive it means their blood calls as the rhesus antigen on them.
what does it mean if someone if rhesus negative?
- If someone is rhesus negative it means their blood cells does not have the rhesus antigen on them.
what is important about rhesus status in pregnancy?
- It is important in one case and that is if the mum if rhesus negative and the baby is rhesus positive.
what happens if you have the rhesus negative antigen and you are pregnancy?
- When you have the rhesus antigen, the body recognises another rhesus antigen to be a part of your body and doesn’t see it as a threat. But if your body see a rhesus negative antigen it will see it as a threat/ pathogen and attack it.
- Your B cells from your immune system will recognise this and create Anti-D antibodies to attack it.
what is the mum is rhesus positive?
- If mum is rhesus positive, there is nothing to worry about as baby can be rhesus positive or negative and the blood cells won’t be attacked.
what if the mum is rhesus negative?
- If the mum is rhesus negative, and baby is rhesus positive then they mum will attack the baby’s blood cells.
what are sensitive events?
Occasions where the baby’s blood may get in the maternal blood stream.
- Miscarriage >12 weeks - Abdominal trauma - At birth
what does the rhesus status mean for current and future pregnancy?
However, this may not affect the pregnancy at the time. We are more concerned about future pregnancies.
what does rhesus negative status mean in future pregnancies?
In future pregnancies, those antibodies the mum developed will be able to cross the placenta and get into baby’s blood stream and destroy the blood cells. As the baby’s blood cells are haemolysis (destroyed) that releases chemicals called bilirubin (jaundice) it can cause significant brain damage. This creates jaundice and haemolytic anaemia which is called haemolytic disease of the newborn or HDN.
how do we prevent issues with rhesus negative status?
We use anti-d via IM infection, at any point where there may have be sensitising events.
what does anti-d do?
What it does it is circulates around the blood destroying any of the babies blood which contains the rhesus antigen. Before the mum has the opportunity to create an immune response.
do rhesus positive women get anti-d?
no
what occasions do rhesus negative women get anti-d?
- Late miscarriage
- Abdominal trauma
- Bleeding
- Routinely at 28 weeks.
- At birth we retrieve blood cord gases to check babies rhesus status and if baby is rhesus positive, we give mum an anti-d infection postpartum. If negative mums don’t need any injection.
what happens in the first contact with rh positive blood?
first contact with rh positive blood, the mother will produce IgM antibodies. These antibodies are big in size and are not able to cross the placenta, so this baby will not be affected. However, once IgM is destroyed, the maternal body will create a template for long-term IgG antibodies. These IgG are smaller and will be able to cross the placenta in future pregnancies. However, this process of creating the template to produce IgG is not that quick: it can take up to 6 months from initial exposure. And it is here where the antiD makes a difference: by artificially giving IgG antibodies, we can prevent maternal body from creating her own IgG template. Without this template, she will not be able to create IgG antibodies herself, and therefore, subsequent rh pos babies will not be at risk.
what are the risks of anti-d?
- It is a blood product
- Around 10% of anti- D crosses the placenta - may generate mild anaemia in the rh pos baby, but it usually require no further treatment
- Allergic reaction to co-adjuvants
what are the three types of blood tests carried out in the context of rh negative blood group?
- Assessing if the mother has become sensitised in the past
- Assessing the risk of anti-D antibodies affecting the baby
- Assessing if the mother has become sensitised after this last pregnancy
what is indirect coombs test?
Indirect Coombs Test
Rh antibodies in maternal blood
Taken from mother antenatally
Sensitisation
what is direct coombs test?
Direct Coombs test
Maternal Rh antibodies in fetal cells
Taken from cord blood
Risk of haemolytic newborn disease
what is kleihauer?
Kleihauer
Fetal cells in a sample of maternal blood
Taken from the mother postnatally
Risk of sensitisation
do women before 12 weeks of pregnancy require anti-d?
Please note that women who have a miscarriage before 12 weeks, they do not require Anti-D rhesus prophylaxis unless:
• they have a surgical procedure to manage a miscarriage (including suspected molar pregnancy) • they have had a surgical procedure to manage an ectopic pregnancy • they have a termination of pregnancy
what are the tayside anti-d doses?
28 Week dose - 1500IU
In case of a sensitising event - 500 IU
what happens if rh negative women have been sensitised in the past?
When women are sensitised against rh positive group, they usually get diagnosed before conception (after a previous pregnancy or a previous blood transfusion). They need to have pre-pregnancy counselling to discuss risks and care plans of future pregnancies.
what happens if rh negative women become pregnant after a being sensitised in the past?
Once they become pregnant, they will be offered non-invasive prenatal testing to check baby’s blood group. If they baby is negative, then no further concerns are raised. If the baby is rh positive, D-antibodies levels will be measured during pregnancy and signs of fetal haemolytic disease will be monitored with regular scans by fetal medicine.
Once baby is born, blood group will be confirmed and baby will be under observations for jaundice and anaemia.
