RBC isoimmunisation

Question 1

What is red blood cell isoimmunisation? (1)

Answer 1

Occurs when the rhesus negative mother mounts an immune response against antigens on rhesus positive fetal red cells that enter her circulation. the resulting antibodies can cross the placenta and cause haemolysis.

Question 2

Name 2 sensitising events. (2)

Answer 2

Delivery, antepartum haemorrhage, miscarriage, ectopic pregnancy, TOP and invasive prenatal testing.

Question 3

Describe the aetiology of rhesus isoimmunisation. (3)

Answer 3

• Sensitising event exposes a rhesus negative mother to a rhesus positive foetus’s red blood cells and maternal antibodies develop.
• This pregnancy is safe as only IgG can cross the placenta.
• In subsequent rhesus positive pregnancies, IgG cross placenta and bind to rhesus antigens causing haemolysis.

Question 4

In rhesus isoimmunisation, how is the fetus affected? (2)

Answer 4

Haemolytic anaemia
Hyperbilirubinaemia
Fetal hydrops (fetal heart failure caused by accumulation of subcutaneous fluid and in body compartments)

Question 5

name 3 complications of rhesus isoimmunisation. (3)

Answer 5

Fetal hydrops
Intrauterine death
Neonatal death
Neonatal kernicterus

Question 6

How can rhesus isoimmunisation be prevented? (2)

Answer 6

Administration of anti-D immunoglobulins at 28 weeks, 34 weeks, after any sensitising event, after delivery.