Rhesus And Other Blood Group Incompatibilities

Question 1

What is the only antibody transferred by the Human Placenta?

Answer 1

IgG via a combo of active and diffusion therefore IgG is often higher in fetus vs mother

Question 2

When can Maternal isoimmunization occur?

Answer 2

May happen after pregnancy during labour or after blood transfusion.

Question 3

Pathogenesis?

Answer 3

Maternal ab attatch themselves to fetal rbc and result in shortened lifespan. Fetus has to posses corrsponding antigen on rbc.

Question 4

How are blood group antigens inherited?

Answer 4

Autosomal Dominant and therefore father is tested for antigen plus allele.

Question 5

Main blood group incompatibikities are?

Answer 5

ABO

Rh

Question 6

When can fetal cells enter maternal circ?

Answer 6

At delivery or abortion
Aph
ECV(turning baby)
C-section

Question 7

What effects can anti D iG have on neonate?

Answer 7

Can be mild with only a positve coombs.

Severe with death in utero due to anaemia and hypoxia

Question 8

Management of a PT who is Rh - without atypical ab?

Answer 8

Fathers blood group and genotype is determined- if he is Rh- then no problems are anticipated.

Mothers blood is tested every 4 weeks after 20 weeks gestation for atypical antigens in case senstiz occurs.

No ab then pt delivered at term.
Rhogam is given if fetus is Rh+ or blood group unknown.

Question 9

When to give Rhogam?

Answer 9

100ug IM

Given when Mother Rh- and after abortion or ectopic.
Not indicated if mother is immunized.

Question 10

How to manage an Rh- patient with atypical Ab?

Answer 10

Check father blood group and genotype

Determine fetal GA and placenta location via U/S.
Estimate mothers Ab titre every two weeks.

Question 11

In a Rh- pt with atyp antibodies what happens if Ab titre is >1:8

Answer 11

U/S examination of MCA. In anaemic fetus due to haemolysis, peak systolic velocity in MCA is increased. This test is repeated 1-2 weekly and if figure rises >1.5 MOM then anaemia is present.

Question 12

What is the plan if anaemia is detected in the fetus?

Answer 12

If fetus is 34weeks or more then delivery is considered.
If fetus is Prem then interuterine blood transfusion is planned and cordocentesis is done to measure Hb immediately.

Transfusion is repeated every 2-3 weeks depending on peak syst velocity in MCA. If no facikities to do transfusion then infant must be delivered after steroid administration.

Question 13

Who should be screened for atypical Ab?

Answer 13

Both Rh- and Rh+ as these ab are found in equal frequency amoung these two groups.

Question 14

What is a blood group incompatibility?

Answer 14

Maternal Antibodies cross the placenta causing fetal haemolytic anaemia.

Antibodies can be naturally ocurring -Igm (anti A or anti B)
OR Atypical and IgG ( anti kidd anti duffy)