Haem: Obstetric Haematology Pt.2 Flashcards
At what point during the pregnancy does platelet count fall most due to ITP?
Platelet count tends to fall dramatically early in pregnancy if present
Does ITP affect the baby?
Yes / Potentially
Anti-platelet IgG can cross the placenta (5-10%). If foetal platelet count drops can increased risk of intracranial haemorrhage. Check platelet count at birth and give IVIG if below 50.
What is mechanism of microangiopathic haemolytic anaemia?
Deposition of platelets and fibrin in microvasculature leading to thrombocytopenia. The deposits can also shear RBCs leading to intravascular haemolysis. Organ damage can also occur due to vessel occlusion
What would you expect to see on the blood film of microangiopathic syndromes?
Schistocytes
Nucleated red cells consistent with increased red cell turnover
What are the causes of MAHA in pregnancy?
- Preeclampsia
- HELLP
- TTP (Thrombotic thrombocytopenic purpura)
- HUS (Haemolytic uraemic syndrome)
- AFLP (Acute fatty liver of pregnancy)
- SLE (Systemic lupus erythema)
- APLS (Antiphospholipid syndrome)
What is HELLP?
Haemolysis
Elevated liver enzymes
Low platelets
What is a leading cause of maternal mortality?
Coagulation changes in pregnancy - VTE
What change in pro- and anti-coagulative factors are seen in pregnancy?
Hypercoagulability
- Factor VIII and vWF - increases x3-5
- Fibrinogen - increases x2
- Factor VII -increases x0.5
Hypofibrinolytic
- Protein S - falls to half basal level
- PAI-1 - increases x5 fold
- PAI-2 produced by the placenta
What is the reason for coagulation changes seen in pregnancy?
Rapid control of bleeding from the placental site (700ml/min) at time of delivery. Coagulation changes control this bleeding.
What are the net effects of coagulation changes seen in pregnancy?
- Increased thrombin generation
- Increased fibrin generation
- Reduced fibrinolysis
- Interact with other maternal factors
This leads to an increased rate of THROMBOSIS
When do coagulation changes in pregnancy return back to normal?
Weeks/months after delivery
When are VTEs most likely to occur?
1-6 weeks post partum
When are deaths due to pulmonary embolism during pregnancy most likely to occur?
A third of cases are post-partum (within 6 weeks post-partum). However, a reasonable proportion also occur in the first trimester.
What investigations for VTE may be done during pregnancy?
Doppler and VQ scans are SAFE to perform in pregnancy CTPA in some cases although increases maternal breast cancer risk
(D-dimer is often elevated in pregnancy so is NOT useful for exclusion of thrombosis)
What are three main factors that increase risk of VTE?
Virchow’s Triad
- Changes in blood coagulation (hypercoaguability)
- Reduced venous return (stasis)
- Vessel wall changes
