Rhesus iso-immunisation
- Rhesus system consists of 3 antigens, C, D and E
- D is most commonly associated with severe haemolytic disease of the newborn
- Occurs if the mother is D rhesus negative and the baby is positive
- 15% of Caucasian population is D rhesus negative
- a similar immune response can be mounted for other RBC antigens, resulting in anti-c and anti-Kell
- Sensitisation may occur via;
- Miscarriage
- Termination
- Antepartum haemorrhage
- Invasive prenatal testing e.g. CVS, amniocentesis)
- Delivery
- Ectopic pregnancy
- Miscarriage
- Doesn’t affect first pregnancy
- In subsequent pregnancy IgG cross placenta causing haemolysis
- Rhesus negative women therefore have regular antibody checks throughout pregnancy
Prevention of rhesus iso-immunisation
- Intramuscular administration of anti-D immunoglobulins to mother within 72hr after exposure to fetal red cells
- Kleihauer test is used to determine the proportion of fetal cells present in the maternal circulation to then calculate the amount of anti-D immunoglobulin required if a large transfusion has occurred
Signs of fetal anaemia
- Polyhydramnios
- Enlarged fetal heart
- Ascites and pericardial effusions
- Oedema (hydrops)
- Hyperdynamic fetal circulation
- Reduced fetal movements
- Abnormal CTG
Spectrum of disease (mild-severe)
- Mild jaundice following normal delivery
- Preterm delivery of fetus requiring exchange transfusion
- Delivery at 34 weeks following biweekly transfusions from 26 weeks
- Stillbirth/neonatal death
Blood transfusion
- Uses concentrated, rhesus negative, CMV negative, irradiated blood
- Injected into umbilical vein