Rhesus Status Flashcards
What is the problem with rhesus status in pregnancy?
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 and a leak of foetal red blood cells occurs, this causes anti-D IgG antibodies to form in the mother. In later pregnancies these can cross placenta and cause haemolysis in the foetus. This can also occur in the first pregnancy due to leaks
How do we prevent sensitisation in mothers who are Rhesus negative?
Test for D antibodies in all Rh -ve mothers at booking. Anti-D should be given to all non-sensitised Rh -ve mothers at 28 and 34 weeks. Anti-D is prophylaxis - once sensitization has occurred it is irreversible.
What should be done if a mother is thought to have had a potentially sensitizing event e.g. a vaginal bleed?
If event is in 2nd/3rd trimester give large dose of anti-D and perform Kleihauer test - determines proportion of foetal RBCs present in the mother.
What events require Anti D immunoglobulin injection?
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 and foetal blood sampling
• Abdominal trauma
What tests should be done on babies born to Rhesus -ve mothers?
All babies born to Rh -ve mother should have cord blood taken at delivery for FBC, blood group & direct Coombs test. If baby is Rh +ve then a Kleihauer test is done and at least 500IU of anti-D is given. Dose can be increased according to the Kleihauer test.
What is the difference between the two Coomb’s tests?
Direct: Is an investigation used to look for autoimmune haemolytic anaemia,
Indirect: Used antenatally to detect antibodies in the maternal blood that can cross the placenta and result in haemolytic disease of the new-born.
How does a Kleihaurer test work?
Kleihauer test (also known as a foetal-maternal haemorrhage test (FMH)) add acid to maternal blood, foetal cells are resistant and so can show the amount of foetal RBC in the mother’s blood. Should be done with any sensitising event after 20 weeks.
How would haemolytic disease of the newborn present?
Oedematous (hydrops fetalis, as liver devoted to RBC production albumin falls)
Jaundice, anaemia, hepatosplenomegaly
Heart failure
Kernicterus brain damage due to jaundice
How should haemolytic disease of the newborn be treated?
Transfusions directly into the umbilical vein, UV phototherapy to remove antibodies
