Rhesus Disease

Question 1

Define Rhesus Disease.

Answer 1

Development of rhesus antibodies in a RhD -ve mother post-exposure to RhD +ve blood cells/antigens.

Question 2

What are the risk factors for rhesus disease?

Answer 2

• Previous pregnancy with insufficient anti-D prophylaxis
• Previous blood transfusion (rare if in UK)

Question 3

What is the pathophysiology of rhesus disease?

Answer 3

1. Rh -ve mother has a Rh +ve child
2. Sensitising event mixes blood - simple SVD is not a sensitising event
3. Mother develops IgM anti-Rh ABs (IgM doesn’t affect 1st baby as IgM cannot cross placenta)
4. Mother delivers or miscarries child
5. Time passes (and mother develops IgG anti-Rh ABs)
6. Mother has a 2nd Rh +ve child
7. Mother’s IgG anti-Rh crosses placenta → hydrops fetalis
   
   1. If child is Rh -ve, there is no problem. However, we assume they are Rh +ve just in case
   2. cffDNA testing can test for the child’s Rh status which reduce the need for anti-D

Pathophysiology = IgG anti-Rh ABs against foetal RBCs → HDN = anaemia + high BR → hydrops fetalis, foetal anaemia, kernicterus

Question 4

What are the sensitising events for rhesus disease?

Answer 4

• PSE = Potentially Sensitising Event
  
  • Amniocentesis, CVS
  • APH/PV bleed in pregnancy
  • ECV
  • Abdominal trauma (T3: 26-37 weeks)
  • Ectopic pregnancy
  • Intrauterine death & stillbirth/TOP/molar pregnancy
  • Intrauterine (transfusion, surgery)
  • Therapeutic miscarriage (any GA, any method)
  • Intra-operative cell salvage
  • Spontaneous miscarriage (>12w GA)
  • Delivery (SCD, CS, instrumental)

Question 5

What are the appropriate investigations for rhesus disease?

Answer 5

• Father status - what blood type could the baby inherit
• Baby status - cffDNA testing
• Mother’s anti-RhD levels - higher = worse
• Kleiheur test - only >20w

Question 6

What is the routine antenatal anti-D prophylaxis?

Answer 6

• Indirect antiglobulin testing at booking
• If indicated either:
  
  • 2 doses of 500 IU at 28 and 34 weeks
  • 1 dose of 1500 IU at 28 weeks
• If mother is found to be RhD -ve and has antibodies at booking → monitor titres and if they peak above a level → monitor baby using Middle Cerebral Artery dopplers weekly → if baby affected, consider IU transfusion

Question 7

What is the prophylactic management for rhesus disease after a sensitising event?

Answer 7

• <72 hours of event → Kleihauer-Bekte (+125 IU IM/1mL foetal blood)
  
  • 250 IU <20 weeks
  • 500 IU >20 weeks

Question 8

What are the complications of rhesus disease?

Answer 8

• Hydrops fetalis
• Intrauterine death
• Neonatal kernicterus