Rhesus negative pregnancy

Question 1

what is the most important antigen in the Rhesus system?

Answer 1

D antigen

Question 2

What happens if a rhesus negative mum delivers a rhesus positive child?

Answer 2

leak of fatal red blood cells

causes anti-D IgG antibodies to form in momma

can cross placenta

cause haemolysis in fetis

Question 3

prevention

Answer 3

anti-D at 28-34 weeks

Question 4

if event occurs in 2nd/3rd trimester what do you do

Answer 4

give large dose of anti-D and perform Kleihauer test - determines proportion of fetal RBCs present

Question 5

when should anti-d be given asap

Answer 5

delivery of a Rh +ve infant, whether live or stillborn

any termination of pregnancy

miscarriage if gestation is > 12 weeks

ectopic pregnancy (if managed surgically, if managed medically with methotrexate anti-D is not required)

external cephalic version

antepartum haemorrhage

amniocentesis, chorionic villus sampling, fetal blood sampling

abdominal trauma

Question 6

ix

Answer 6

all babies born to Rh -ve mother should have cord blood taken at delivery for FBC, blood group & direct Coombs test

Coombs test: direct antiglobulin, will demonstrate antibodies on RBCs of baby

Kleihauer test: add acid to maternal blood, fetal cells are resistant

Question 7

affected fetes features

Answer 7

oedematous (hydrops fetalis, as liver devoted to RBC production albumin falls)
jaundice, anaemia, hepatosplenomegaly
heart failure
kernicterus

Question 8

Mx of affected fetus

Answer 8

transfusions

UV phototherapy