Antenatal - Rhesus incompatibility

Question 1

explain the significance of Rhesus incompatibility in pregnancy

Answer 1

when a women is rhesus-D negative child may be rhesus positive. at some point like childbirth, blood from the baby may find its way into the mothers bloodstream. the mothers immune system will then recognise the rhesus-D antigen as foreign and produce antibodies to the rhesus-D antigen

not a problem in the first pregnancy

in subsequent pregnancies the mothers anti-rhesus D antibodies can cross the placenta and if the fetus is rhesus-D positive, the antibodies will attach themselves to the RBC of the fetus and cause immune system of the fetus to attack them = haemolysis

haemolytic disease of the newborn

Question 2

what is the management of rhesus incompatibility?

Answer 2

prevention of sensitisation - intramuscular anti-D injections to rhesus-D negative women

no way to reverse sensitisation

Question 3

how does the anti-D medication work?

Answer 3

attaches itself to the rhesus-D antigens on the fetal RBC in the mothers circulation causing them to be destroyed which prevents the mothers immune system recognising the antiogen and creating it’s own antibodies to the antigen

acts as a prevention for the mother becoing sensitised to the rhesus-D antigen

Question 4

when are anti-D injections given?

Answer 4

routinely - 28 weeks gestation, birth (if baby is rhesus +ve)

anytime where sensitisation may occur

within 72 hours of sensitisation

Question 5

what counts as a sensitisation event?

Answer 5

bleeding before 12 weeks - heavy, persistent or painful

any APH after 12 weeks

CVS/amniocentesis

ECV

IUD

ectopic, molar, evacuation of RPC, miscarriage

abdominal trauma

Question 6

what is the Kleinhauer test?

Answer 6

checks how much fetal blood has passed into the mothers blood during a sensitisation event.

used after any sensitisation event after 20 weeks gestation to assess whether further doses of anti-D is required

Question 7

how is the Kleihauer test carried out?

Answer 7

adding acid to a sample of the mothers blood. fetal haemoglobin is naturally more resistant to acid so that they are protected against acidosis that occurs around childbirth

fetal haemoglobin persists in response to acid while the mothers haemoglobin is destroyed

Question 8

symptoms of haemolytic disease of the newborn baby

Answer 8

• kernicterus
• anaemia
• hydrops fetails
  
  • congestive cardiac failure

Question 9

if you think there has been exposure umbilical artery sampling and amniocentesis

Answer 9

low haemoatocrit

positive coombs test