Anaemia in Pregnancy + Rhesus Status Flashcards
What is anaemia?
a low concentration of haemoglobin in the blood
- this is the result of an underlying disease and is not a disease itself
What is the importance of haemoglobin?
What is important for ensuring its functioning?
- it is a protein found in RBCs
- it is responsible for picking up oxygen in the lungs and transporting it to cells
- iron is essential for creating haemoglobin / is part of its structure
When are women screened for anaemia during pregnancy?
- booking clinic
- 28 weeks gestation
Why does anaemia occur in pregnancy?
- during pregnancy, the plasma volume increases
- this leads to a reduction in haemoglobin concentration
the blood is diluted due to an increased plasma volume
Why is it important to optimise treatment of anaemia during pregnancy?
it is important to ensure the woman has reasonable reserves in case there is significant blood loss during delivery
How does anaemia present?
- it is often asymptomatic
- it may present with:
- SOB
- pallor
- fatigue
- dizziness
What are the normal ranges for haemoglobin at booking, 28 weeks gestation and postpartum?
Booking:
- Hb should be > 110 g/L
28 weeks gestation:
- Hb should be > 105 g/L
Post-partum:
- Hb should be > 100 g/L
How can the mean cell volume (MCV) be used to determine the cause of anaemia?
Low MCV:
- indicates iron deficiency anaemia
Normal MCV:
- indicates physiological anaemia due to increased plasma volume of pregnancy
Raised MCV:
- indicates B12 or folate deficiency
(MCV = a measurement of RBC size)
What other routine screening is offered to women at booking clinic?
haemoglobinopathy screening
- all women are offered screening for thalassaemia
- high risk women are offered screening for sickle cell disease
(these would both cause significant anaemia during pregnancy)
What investigations that are NOT routinely performed may help to identify the cause of the anaemia?
- ferritin
- B12
- folate
What is the management for anaemia in pregnancy?
iron replacement
- typically, 200mg ferrous sulphate 3x daily
- women who are not anaemic but have low ferritin stores may be started on supplementary iron
What are women with a low B12 in pregnancy tested for?
pernicious anaemia
- this involves testing for intrinsic factor antibodies
How does pernicious anaemia occur?
- autoimmune condition in which autoantibodies attack parietal cells that make intrinsic factor
- intrinsic factor is needed for the absorption of vitamin B12 in the gut
- malabsorption of B12 means that not enough RBCs are made
(can also occur due to conditions affecting the stomach / small intestine that reduce absorption of B12)
What are the treatment options for low B12?
- IM hydroxycobalamin injections
- oral cyanocobalamin tablets
What is the management for women with folate deficiency?
- all women should be taking 400mcg folic acid daily
- this is increased to 5mg if there is folate deficiency
How is thalassaemia / sickle cell disease managed in pregnancy?
- high dose folic acid (5mg)
- close monitoring / regular transfusions when required
What Rhesus status means no further treatment is required in pregnancy?
Rhesus-D positive
- if the mother is Rh-D positive, no additional treatment is needed
What happens if a rhesus-D negative woman becomes pregnant with a rhesus-D positive fetus?
- at some point during the pregnancy, the blood from the baby will enter the mother’s bloodstream
- the RBCs of the fetus display the Rh-D antigen
- the mother’s immune system produces antibodies against the Rh-D antigen
- the mother has now become sensitised to the Rh-D antigen
What happens if a rhesus-D negative woman becomes pregnant with a rhesus-D positive fetus?
- at some point during the pregnancy, the blood from the baby will enter the mother’s bloodstream
- the RBCs of the fetus display the Rh-D antigen
- the mother’s immune system produces antibodies against the Rh-D antigen
- the mother has now become sensitised to the Rh-D antigen
What issues are caused by Rhesus sensitisation in a first pregnancy?
sensitisation does NOT cause problems in a first pregnancy
What is the issue that arises from Rhesus sensitisation in subsequent pregnancies?
- the woman now has antibodies against the Rh-antigen
- if the second fetus is Rh positive, the antibodies cross the placenta
- the antibodies attach to the fetal RBCs and cause the fetal immune system to destroy them
- this results in haemolytic disease of the newborn
What is involved in the management of Rhesus incompatibility?
- management is aimed at preventing sensitisation
- intramuscular anti-D injections are given the Rh-negative women
- once sensitisation has occurred, there is no way of reversing it
How do the anti-D injections work?
- the anti-D attaches to the rhesus D antigens of the fetal RBCs within the maternal circulation
- this causes them to be destroyed
- as the fetal RBCs are destroyed, this prevents the mother’s immune system from recognising the Rh-D antigen and creating antibodies against it
When are anti-D injections given?
Routine injections:
- 28 weeks gestation
- during birth (if blood group of fetus is Rh+)
Additional injections given at any time sensitisation may occur:
- antepartum haemorrhage
- amniocentesis
- abdominal trauma
When should anti-D be given when a sensitisation event occurs?
Anti-D must be given within 72 hours of a sensitisation event
What test is performed to determine whether further anti-D is required?
Kleihauer test
Why and when is the Kleihauer test performed?
- it assesses how much fetal blood has passed into the mother’s blood during a sensitisation event
- it is used to assess any event after 20 weeks gestation
- it assesses whether further doses of anti-D are required
How does the Kleihauer test work?
- acid is added to a sample of the mother’s blood
- fetal haemoglobin is more resistant to acid
- fetal Hb persists in response to the acid, whereas the mother’s Hb is destroyed
- the number of cells still containing Hb (fetal cells) can then be calculated
