Powerpoint 3 - Resus incompatabiloty Flashcards
What does the term “rhesus” refer to in blood typing?
It refers to various types of rhesus antigens on the surface of red blood cells, separate from the ABO blood group system.
What is the most relevant antigen in the rhesus blood group system?
The most relevant antigen within the rhesus blood group system is the rhesus-D antigen. When we refer to someone’s rhesus status in relation to pregnancy (e.g. “she is rhesus-negative”), we are usually referring to whether they have the rhesus-D antigen present on their red blood cell surface.
What does it mean when someone is referred to as “rhesus-negative”?
It means they do not have the rhesus-D antigen on their red blood cell surface.
Do rhesus-D positive women need special treatment during pregnancy?
No, they do not need additional treatment.
Why is rhesus-D status important in pregnancy?
If a rhesus-D negative mother carries a rhesus-positive baby, the mother’s immune system may produce antibodies against the baby’s red blood cells, potentially leading to haemolytic disease of the newborn in future pregnancies.
What is haemolytic disease of the newborn?
It occurs when a mother’s anti-rhesus-D antibodies destroy the red blood cells of a rhesus-positive fetus, causing haemolysis.
What is the main method to prevent rhesus sensitisation during pregnancy?
Giving intramuscular anti-D injections to rhesus-D negative women.
How does anti-D medication work?
It attaches to fetal rhesus-D antigens in the mother’s circulation, causing their destruction and preventing the mother from producing her own antibodies.
When are routine anti-D injections given during pregnancy?
At 28 weeks gestation and at birth (if the baby is rhesus-positive).
Name situations when anti-D should ALSO be given outside routine times.
Antepartum haemorrhage, amniocentesis, abdominal trauma, or any other sensitising event.
What is the Kleihauer test used for?
The Kleinhauer test is performed to see how much fetal blood has passed into the mother’s blood, to determine whether further doses of anti-D are required.
How does the Kleihauer test work?
Acid is added to the mother’s blood sample; fetal haemoglobin resists the acid, while maternal haemoglobin is destroyed. The remaining fetal cells are then counted.
What is meant by sensitising event ?
A sensitising event refers to any situation during pregnancy or childbirth where fetal blood can mix with the mother’s blood. This mixing can lead to the mother’s immune system being exposed to the fetal rhesus-D antigens (if present), potentially causing her to develop antibodies against them.
Examples of sensitising events include:
Antepartum haemorrhage: Bleeding from the uterus during pregnancy.
Amniocentesis or other invasive procedures: These can inadvertently introduce fetal blood into the maternal circulation.
Abdominal trauma: Physical injury to the abdomen can cause fetal and maternal blood to mix.
Miscarriage or stillbirth: These events may involve fetal blood entering the mother’s circulation.
Childbirth: The most common time for mixing of maternal and fetal blood.
Preventing sensitisation in these events is critical, which is why anti-D immunoglobulin is often administered after any such occurrence.
How does a baby have a resus positive baby if she is resus negative ?
why is sensitisation more common in second pregnancy?
Usually, this sensitisation process does not cause problems during the first pregnancy. During subsequent pregnancies, the mother’s anti-rhesus-D antibodies can cross the placenta into the fetus. If that fetus is rhesus-D positive, these antibodies attach themselves to the red blood cells of the fetus and causes the immune system of the fetus to attack them, causing the destruction of the red blood cells (haemolysis). The red blood cell destruction caused by antibodies from the mother is called haemolytic disease of the newborn.
