Rhesus incompatibility

Question 1

what is rhesus?

Answer 1

there are lots of rhesus antigens on the surface of RBC (most common is D)

if someone is rhesus positive, they have D antigen

if they are rhesus negative they do not have the D antigen. if they become exposed to that antigen then they will make anti-D antibodies

Question 2

rhesus D negative

Answer 2

if a pregnant woman is rhesus - D negative (does not have the D antigen) then consideration must be given to the possibility of her child being rhesus positive.

in labour, it is likely she will become ‘exposed’ to the child’s D antigens and therefore the mother will become sensitised and produce antibodies. this doesn’t cause problems during the first pregnancy but will do in subsequent pregnancies if fetus is rhesus-D positive.

the antibodies attach themselves to fatal RBC and causes attack - haemolysis= haemolytic disease of the newborn

Question 3

management of rhesus antibodies

Answer 3

IM anti-D injections to rhesus-D negative women

anti-D works by attaching itself to the antigens on fatal RBC and causes them to be destroyed before mother’s immune system recognises them

can be given at 28 weeks and birth.

any other time where sensitisation may have occurred (within 72 Horus of sensation event)
Antepartum haemorrhage
Amniocentesis procedures
Abdominal trauma

Question 4

Kleinhauer test

Answer 4

this can be done within 72 hours of sensitisation, after 20 weeks gestation, to determine how much fatal blood has passed into mom’s blood and whether further does of anti-D are needed.

add acid to sample of mum’s blood. fatal haeoglobin is more resistant to acid so will persist in response to the added acid (mom’s will be destroyed)