Rhesus Negative Pregnancy

Question 1

The Rhesus system is the second most important antigen system in the found in the red blood cells. What is the first?

Answer 1

The ABO system.

Question 2

What is the most important antigen in the rhesus system?

Answer 2

The D Antigen

Question 3

Describe the pathophysiology of anti-D igG antibodies forming in the mother.

Answer 3

If a Rh -ve mother delivers a Rh +ve child a leak of fetal red blood cells may occur this causes anti-D IgG antibodies to form in mother. In later pregnancies, these can cross the placenta into the fetus and cause hemolysis in the fetus.

Question 4

What percentage of mothers are rhesus negative?

Answer 4

15%

Question 5

Once sensitization in the mother has occured (anti-D IgG antibodies being formed) can it be reversed?

Answer 5

No

Question 6

How do we prevent this from happening?

Answer 6

1. Test all Rh -ve mothers at booking
2. Routine Antenatal Anti-D Prophylaxis (RAADP
   
   1. Non-sensitized Rh-ve mothers are given anti-D at either:
      
      1. Double dose: 28 weeks & 34 weeks. Dose is 500iu IM (NICE Recommends)
      2. Single Dose: Between 28-30 weeks: Dose 1500iu IM.

Question 7

What is a PSE and give examples?

Answer 7

In the case of a potentially sensitising event (PSE) during pregnancy

• Delivery of a Rh +ve infant, whether live or stillborn
• Any termination of pregnancy
• Miscarriage if gestation is > 12 weeks
• Ectopic or Molar pregnancy
• External cephalic version
• Antepartum haemorrhage/bleeding in pregnancy.
• Amniocentesis, chorionic villus sampling, fetal blood sampling
• Abdominal trauma

Question 8

If a PSE occurs in the first 20 weeks of pregnancy, what should you do?

Answer 8

Administer at least 250 IU of anti-D ig within 72 hours of the event.

Question 9

If a PSE occurs in the after 20 weeks of pregnancy, what should you do?

Answer 9

Administer 500IU of anti-D Ig within 72 hours

&

Do an FMH (Fetal Maternal Haemorrhage) (a.k.a. Kleihauer Test)

Then administer more anti-D Ig following discussion with the laboratory.

Question 10

What blood test should be done at the birth of babies born to Rh -ve mothers?

Answer 10

Cord Blood to determine:

FBC, Blood Group and DAT.

Question 11

What are some features of a haemolytic disease of the newborn?

Answer 11

• Oedematous (hydrops fetalis, as liver devoted to RBC production albumin falls)
• Jaundice, anaemia, hepatosplenomegaly
• Heart failure
• Kernicterus

Question 12

What is the treatment for haemolytic disease of the newborn?

Answer 12

Blood transfusions

UV phototherapy