Rhesus Isoimmunisation

Question 1

Define rhesus isoimmunisation?

Answer 1

Mother mounts an immune response (sensitisation) against antigens on the foetal RBCs that enter her circulation. Her Antibodies from the immune response pass into the placenta and destroy foetal RBCs

Question 2

When is rhesus isoimmunisation clinically relevant?

Answer 2

If the baby is Rhesus Positive (+) and the mother is Rhesus Negative (-)

Question 3

Why is rhesus disease a particular concern for future pregnancies?

Answer 3

Immunity is permanent - if the mother’s sensitised immune system is re-exposed to foetal RBC (+) Antigens an immediate and large number of antibodies will be created - crossing the placenta and destroying RBCs

Question 4

Name two other similar red blood cell antibodies that are clinically relevant?

Answer 4

Anti-Kell

Anti-C

Question 5

In mild forms of rhesus disease - what complications may present?

Answer 5

There may only be neonatal jaundice - however with progression and enough haemolysis = anaemia

Question 6

In more moderate/severe forms of rhesus disease - what complications may present?

Answer 6

Haemolysis can lead to foetal cardiac failure

Ascites/oedema = foetal hydrops and subsequently death

Question 7

Name three risk factors associated with rhesus disease?

Answer 7

FHx
Previous rhesus disease
Caucasian

Question 8

At which point is the mother screened?

Answer 8

Antibodies checked at:
Booking appointment
28 week check

Question 9

What treatment can be used to prevent rhesus haemolytic disease?

Answer 9

ANTI-D - exogenously given to ‘mop up’ any foetal RBCs that cross into maternal blood stream - preventing the mother mounting an immune response and becoming sensitised

Question 10

Describe the indications for usage of ANTI-D?`

Answer 10

If maternal Anti-D is already present then sensitisation has already occurred and treatment becomes pointless
1500 IV units given to ALL mothers Rh(-) at 28 weeks

Question 11

Describe the investigation used to assess the number of foetal RBCs that have crossed into the maternal circulation?

Answer 11

Kleihauer test

Question 12

How can the severity of foetal anaemia be assessed?

Answer 12

Ultrasound + doppler of the middle cerebral artery -

Very severe if

Question 13

If foetal anaemia is suspected what investigation should be carried out?

Answer 13

Foetal blood should be sampled via ultrasound guided needle into the umbilical cord