Rhesus -ve Pregnancy

Question 1

what is the most important antigen of the rhesus system found on RBCs?

Answer 1

D-antigen

Question 2

what happens when a Rh -ve mother delivers a Rh +ve child?

Answer 2

a leak of fetal RBCs may occur => causes anti-D IgG antibodies to form in mother

=> crosses placenta in later pregnancies => causes haemolysis in fetus

Question 3

how do we prevent complications from a Rh -ve pregnancy from happening?

Answer 3

1. test for D antibodies in all Rh -ve mothers at booking
2. give anti-D to non-sensitised Rh -ve mothers at 28 and 34 weeks
3. anti-D is prophylaxis – once sensitisation has occurred, it is irreversible
4. if event is in 2nd/3rd trimester, give large dose of anti-D and perform Kleihauer test – determines proportion of fetal RBCs present

Question 4

when should you give anti-D immunoglobulin?

Answer 4

should be given ASAP (but always within 72 h) in the following situations:

1. delivery of a Rh +ve infant, whether live/stillborn
2. any TOP
3. miscarriage if gestation >12 wks
4. ectopic pregnancy (if mx surgically only; if mx medically with methotrexate, anti-D not required)
5. external cephalic version
6. APH
7. amniocentesis, CVS, FBS
8. abdominal trauma

Question 5

what should be done for all babies born to a Rh -ve mother?

Answer 5

1. cord blood taken at delivery for FBC, blood group, direct Coombs test
2. Coombs test: direct antiglobulin, will demonstrate antibodies on RBCs of baby
3. Kleihauer test: add acid to maternal blood, fetal cells are resistant

Question 6

what are the signs that could be seen in the affected fetus of a Rh -ve pregnancy?

Answer 6

1. oedematous (hydrops fetalis, as liver devoted to RBC production, albumin falls)
2. jaundice, anaemia, HSM
3. heart failure
4. kernicterus

Question 7

how do you treat affected fetus of Rh -ve pregnancy?

Answer 7

• transfusions
• UV phototherapy