Rhesus_Negative_Pregnancy_Flashcards
What is the significance of the D antigen in the Rhesus system?
The D antigen is the most important antigen of the Rhesus system, and along with the ABO system, it is the most important antigen found on red blood cells.
What percentage of mothers are Rhesus negative (Rh -ve)?
Around 15% of mothers are Rhesus negative.
What happens if a Rh -ve mother delivers a Rh +ve child?
A leak of fetal red blood cells may occur, causing anti-D IgG antibodies to form in the mother. In later pregnancies, these antibodies can cross the placenta and cause haemolysis in the fetus.
When should anti-D immunoglobulin be given to Rh -ve mothers?
Anti-D immunoglobulin should be given at 28 and 34 weeks to non-sensitised Rh -ve mothers. It should also be given as soon as possible (within 72 hours) in situations such as delivery of a Rh +ve infant, termination of pregnancy, miscarriage > 12 weeks, ectopic pregnancy (if managed surgically), external cephalic version, antepartum haemorrhage, amniocentesis, chorionic villus sampling, fetal blood sampling, and abdominal trauma.
What is the purpose of the Kleihauer test?
The Kleihauer test determines the proportion of fetal RBCs present by adding acid to maternal blood. Fetal cells are resistant to the acid.
What tests should be performed on all babies born to Rh -ve mothers?
Cord blood should be taken at delivery for FBC, blood group, and direct Coombs test.
What does the Coombs test demonstrate?
The Coombs test (direct antiglobulin) demonstrates antibodies on the RBCs of the baby.
What are the clinical features of an affected fetus in a Rh -ve pregnancy?
Oedematous (hydrops fetalis), jaundice, anaemia, hepatosplenomegaly, heart failure, kernicterus.
What is the treatment for an affected fetus in a Rh -ve pregnancy?
Transfusions and UV phototherapy.
summarise
Rhesus negative pregnancy
A basic understanding of the pathophysiology is essential to understand the management of Rhesus negative pregnancies
along with the ABO system the Rhesus system is the most important antigen found on red blood cells. The D antigen is the most important antigen of the rhesus system
around 15% of mothers are rhesus negative (Rh -ve)
if a Rh -ve mother delivers a Rh +ve child a leak of fetal red blood cells may occur
this causes anti-D IgG antibodies to form in mother
in later pregnancies these can cross placenta and cause haemolysis in fetus
this can also occur in the first pregnancy due to leaks
Prevention
test for D antibodies in all Rh -ve mothers at booking
NICE (2008) advise giving anti-D to non-sensitised Rh -ve mothers at 28 and 34 weeks
the evidence base suggests that there is little difference in the efficacy of single-dose (at 28 weeks) and double-dose regimes (at 28 & 34 weeks). For this reason the RCOG in 2011 advised that either regime could be used ‘depending on local factors’
anti-D is prophylaxis - once sensitization has occurred it is irreversible
if event is in 2nd/3rd trimester give large dose of anti-D and perform Kleihauer test - determines proportion of fetal RBCs present
Anti-D immunoglobulin should be given as soon as possible (but always within 72 hours) in the following situations:
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
Tests
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
Affected fetus
oedematous (hydrops fetalis, as liver devoted to RBC production albumin falls)
jaundice, anaemia, hepatosplenomegaly
heart failure
kernicterus
treatment: transfusions, UV phototherapy
A 30-year-old woman who is 26 weeks pregnant is admitted to the maternity unit with heavy vaginal bleeding. She is Rhesus negative.
What is the most appropriate management for prophylaxis of Rhesus sensitisation?
One dose of Anti-D immunoglobulin, Kleihauer test not required
Routine Anti-D immunoglobulin prophylaxis at 28 weeks
One dose of Anti-D immunoglobulin followed by a Kleihauer test
No Anti-D immunoglobulin required
Anti-D immunoglobulin infusion
One dose of Anti-D immunoglobulin followed by a Kleihauer test
This is a question about the prophylaxis of Rhesus sensitisation in a Rhesus negative Mother with antepartum haemorrhage.
Antepartum haemorrhage is associated with fetomaternal haemorrhage (FMH) and therefore an increased risk of Rhesus sensitisation and Rhesus disease of the newborn in subsequent pregnancies.
The correct answer is one dose followed by a Kleihauer test.
A Kleihauer test is a test for FMH which detects fetal cells in the maternal circulation and, if present, estimates the volume of FMH to allow calculation of additional anti-D immunoglobulin. According to BCSH guidelines, it is required for any sensitising event after 20 weeks gestation.
Although the routine prophylaxis at 28 weeks can and should still go ahead, anti-D needs to be given immediately. There is no such thing as an anti-D immunoglobulin infusion.
Source: British Committee for Standards in Haematology - guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn.
