Rhesus incompatibility in pregnancy 27/09

Question 1

What is ABO incompatibility?

Answer 1

-Potential for ABO isoimmunisation with maternal group O and fetal group A or B. Caused by the igG anti A or B antibodies. occurs in maternal circulation and can occur in the first pregnancy.

Question 2

what is rhesusisoimmunisation?

Answer 2

-Occurs as a result of fetomaternal haemorrhage detected by kliehauer blood test.

Question 3

How does rhesus isoimmunisation occur?

Answer 3

Maternal immune system produced b lymphocyte clones which recognise the RhD antigen.
IgM produced
followed by IgG anti D
Memory B lymphocytes are also produced
Attacks fetal RBC’s in next pregnancy causing anaemia and potentially haemolytic disease of the newborn.

Question 4

What happens once sensitisation has occurred?

Answer 4

Response to further exposure to fetal RBC is more rapid

• IgG Anti D antibodies produced after 1-2 weeks and cross the placenta.
• Antibodies coat fetal erythrocytes
• Cause premature clearance resulting in fetal anaemia.

Question 5

What is routine prophylaxis for rhesus incompatibility?

Answer 5

• 1 or 2 doses of anti-d antenatally

- 500IU at 28 weeks and 34 weeks or 1500IU at 28 weeks

Question 6

When would you take a Kliehaur test?

Answer 6

• past 20 weeks gestation to give a minimum of anti-d 500IU. If not 20 weeks don’t need lkiehour and give 250Iu AntiD.

Question 7

What should you do with women presenting with continuous uterine bleeding?

Answer 7

-Minimum 500 IU 6 weekly intervals. Kliehauer every two weeks to monitor fetal maternal transfusion.

Question 8

Why is it given IM into the deltoid muscle?

Answer 8

gluteal delays absorption

Question 9

What occurs with postnatal prophylaxis?

Answer 9

• Cord blood is obtained for ABO group, Rh D type
• Maternal blood ABO group RH D and Kliehauer.
• 500iu Anti-D recommended within 72 hours to all women with Rh D+ve baby.
• Kliehauer result may indicate need for a higher dose

Question 10

What care is provided for rhesus sensitised women?

Answer 10

• Close monitoring of D-antibody levels 4 weekly up to 28weeks then subsequently 2 weekly. Rising levels review by fetal medicine team alongisde USS.
• Monitoring is to detect fetal anaemia.

Question 11

What is the next step is USS identifies signs of fetal anaemia?

Answer 11

• Fetal blood sampling is indicated. Ultrasound guided cordocentesis. If the fetal haemocrit it the same or <30 intrauterine transfusion is considered.
• o-ve packed ells aim to gradually increase the haemocrit to 40-50%.