Rhesus Haemolytic Disease

Question 1

What is the difference between isoimmunisation and alloimmunisation?

Answer 1

Isoimmunisation

maternal antibodies develop against fetal red blood cells. These cross to the fetus and my lead to haemolysis (and associated complications).

Alloimmunisation

IM injection of anti-D, provides passive immunisation of a non-sensitised woman around the time of exposure to RhD. Prevents isoimmunisation.

Question 2

What is the pathophysiology of Rhesus Haemolytic Disease?

Answer 2

1. Child has Rh+ blood type (heterozygous due to paternal genes), while mother is Rh+.
2. Fetal-maternal haemorrhage.
3. Generation of IgM antibodies on first exposure.
4. On further exposure of fetal blood cells (2nd pregnancy) - IgG antibodies formed. Cross the placenta and cause hemolysis of the fetal RBC, causing fetal anemia and further complications (see other flashcards/OneNote).

Question 3

What are the possible causes of fetomaternal haemorrhage?

Answer 3

• labor
• antepartum haemorrhage
• external cephalic version
• trauma (ie, mva)
• amniocentesis/cvs
• miscarriage
• ectopic pregnancy
• miscarriage
• partial molar pregnancy
• silent f-m haemorrhage

Question 4

What are the effects of fetal hemolysis (due to antibody attack) on the fetus

Answer 4

ANEMIA: –>

Liver

• portal HTN
• hepatosplenomegaly.

Circulatory

• Hyperdynamic circulation
• CCF
• cardiac compromise
• hypoviscosity

Tissues

• tissue hypoxia
• increased brain perfusion
• hydrops fetalis (sometimes assoc with polyhydramnios)

FDIU!!

Question 5

What signs do you look for to identify fetal anemia - seen on MCA doppler, CTG and US

Answer 5

MCA Doppler:

• hyperdynamic circulation (Increased HR)

= increased peak velocity

reliable < 34 weeks

US

• hydrops fetalis (ascites, pericardial effusion) + polyhydramnios
• enlarged fetal heart

CTG

• reduced movements
• increased HR
• abnormal: reduced variability, sinusoidal trace)

Question 6

What investigations are carried out antenatally to prevent hemolytic disease?

Answer 6

First antenatal test (19-20 weeks): Blood group and antibody screen (G+S).

If Rh+ - nothing.

If Rh- :

• further G+S at 28 weeks + 34 weeks.
• IgG antibodies at 28 + 34 weeks.

Consider

• Fetal surveillance (US, CTG, MCA doppler)
• Paternal blood type (gives idea of likelihood of baby’s blood type)
• Cord sampling (Kleihauer test - if further antibodies needed).
• NIPT: to determine blood type of baby.

Question 7

What is the management if an elevated MCA flow or amniotic biliruben levels are found to be high?

Answer 7

Intravascular intrauterine blood transfusion.

If very serious (hydrops etc ) - deliver at 28 weeks.

Question 8

What is the prognosis, in hydrops fetalis vs non hydrops fetalis?

Answer 8

If no hydrops - fetuses undergoing IUT >90%,

If hydrops - 75% survival.