Rhesus isoimmunisation

Question 1

Sensitisation

Answer 1

Small amounts of foetal blood cross placenta
If foetus anti-D positive and mother anti-D negative, mother will recognise as foreign and mount immune response => anti-D antibodies

Question 2

Haemolysis

Answer 2

Immunity is permanent
Subsequent pregnancies, large numbers of antibodies rapidly created
They cross placenta and bind to foetal RBC, which are destroyed
This causes haemolytic anaemia and death, called haemolytic disease

Question 3

Potentially sensitising events

Answer 3

TOP
Evacuation of retained products of conception after miscarriage
Ectopic pregnancy
Vaginal bleeding >12 weeks
Heavy vaginal bleeding
External cephalic version
Invasive uterine procedure (eg amniocentesis, chorionic villus sampling)
Intrauterine death
Delivery

Question 4

Prevention

Answer 4

Exogenous anti-D after potentially sensitising events to ‘mop up’ foetal red cells and prevent an immune response
Given to: all women who are Rh- at 28 weeks; Rh- women who have a potentially sensitising event; within 72h of delivery if baby Rh+

Question 5

Manifestations

Answer 5

Neonatal jaundice
Haemolytic disease of the newborn
Severe cases: intrauterine anaemia => heart failure, ascites and oedema (hydrops)
Worse with each pregnancy

Question 6

Management

Answer 6

Identification of women at risk of foetal haemolysis
Assessment of whether foetus is anaemic (fortnightly Doppler/foetal hydrops, then foetal blood sampling)
Treatment of foetal anaemia: in untero transfusion; delivery >36w