Rhesus

Question 1

Types of rhesus antibodies, which chromosome they are found on, and which of the two are problematic

Answer 1

Rhesus C, D and E - on chromosome 1

Rhesus D > rhesus C

Question 2

If you are rhesus negative, what does this mean?

Answer 2

Homozygous for recessive alleles, or one of the two genes has been deleted

Question 3

What disease results from rhesus incompatibility?

Answer 3

Haemolytic disease of the foetus and newborn

Question 4

Rhesus isoimmunisation

Answer 4

Rhesus negative mother gets exposed to a rhesus positive baby.
Exposure must be significant (e.g. SVD is not adequate to mount a response)
The second exposure from a second rhesus positive baby mounts a stronger response

Question 5

Why does the primary exposure/response not result in HDFN? Why does the second exposure result in HDFN?

Answer 5

IgM doesn’t cross placenta
IgG does

Question 6

List some potential sensitising events

Answer 6

Placental abruption
Trauma

Types of pregnancies going wrong/needing abortion:

Ectopic pregancy
Molar pregnancy evacuation
Miscarriage
TOP
IU death, still birth

Any IU intervention:

Amniocentesis
Chorionic villus sampling
ECV
Transfusion

Delivery:
Instrumental, c-section, sometimes normal delivery

Question 7

Symptoms of HDFN

Answer 7

Reduced fetal movements
Reduced variability on CTG
Abnormal CTG, showing a sinusoidal trace eventually
Polyhydramnios
Enlarged foetal heart
Ascites, pericardial effusions
Hyperdynamic circulation detected on Doppler USS

Question 8

Investigations

Answer 8

Basic obs
Urine dip
Bloods - FBC, cross match, group and save, antibodies, CTG, foetal USS
Baby status -cffDNA
Kleihauer test

Question 9

When do you do cell-free foetal DNA testing?

Answer 9

At 12 weeks to determine baby’s Rhesus status

Question 10

When do you administer anti-D prophylaxis normally

Answer 10

28 and 34 weeks