Rhesus isoimmunization

Question 1

Definition of RI

Answer 1

1. Maternal antibody response is mounted against the fetal blood cells.
2. IgG antibodies cross the placenta and cause fetal red blood cell destruction.

Question 2

Pathophysiology of Rhesus disease

Answer 2

1. Fetal cells cross over into the maternal circulation in normal pregnancy
2. Fetus red blood cells may carry Rhesus D antigen whereas the mother does not.
3. Indivisuals exposed to foreign antigen for the first time mount a response with IgM antibodies
4. Re exposure results in IgG antibodies produced
5. Cross over the placenta and cause haemolytic anaemia

Question 3

What is sensitisation?

Answer 3

Individual exposed to foreign antigen the first time produces IgM antibodies
- IgM antibodies cannot cross over the placenta so pregnancy is not at risk

Question 4

Milder cases of hemolytic anaemia can cause

Answer 4

Neonatal anaemia or jaundice from increased bilirubin levels

Question 5

Potential sensitizing events for Rhesus disease

Answer 5

1. TOP/ERCP
2. Ectopic pregnancy
3. Vaginal bleeding > 12 weeks
4. Invasive procedure/trauma
5. Extracephalic version
6. Delivery

Question 6

When should women be checked for Rhesus antibodies?

Answer 6

1. 28 weeks

2. 34 weeks

Question 7

Prevention of Rhesus disease

Answer 7

Anti D immunoglobulin is given to the mother

• binds to any fetal cells in her circulation carrying D antigens
• prevents immune system recognizing them thus no immune response is being initiated

Question 8

When should Anti D be given?

Answer 8

1. Routinely at 28 weeks
2. Within 72 hours of any sensitising event
3. After delivery if fetus is found to be RhD +