8.8 Rhesus Incompatibility

Question 1

Who gets injured how in a rhesus incompatibility?

Answer 1

If a rhesus negative mother is sensitised to rhesus D she will have developed antigen against rhesus D. Theses antigens can cross the placenta and damage a rhesus positive baby (often a different pregnancy to the sensitisation event).

This leads to haemolysis and anaemia in foetus and haemolytic disease of the newborn.

Question 2

How is rhesus incompatibility avoided?

Answer 2

Anti-D injections in rhesus negative mothers.

(Anti-D binds to rhesus antigens on fetal cells in mothers circulation and gets them destroyed before mother develops antibody)

Question 3

When are anti-D injections given?

Answer 3

• 28 weeks and /or 34 weeks
• at birth

Within 72 hrs of any sensitisation event:

• antepartum haemorrhage
• amniocentesis procedures
• abdo trauma

Question 4

What test is performed after possible rhesus sensitisation event?

Answer 4

Kleihauer test if past 20 weeks

Tests how much RBCs from foetus are in mothers blood, add acid - fetal cells are more resistant to acid.