Haematology 9 - Obstetric haematology Flashcards
What change in Hb concentration occurs in pregnancy and why?
Lower concentration (mild anaemia)
Red cell mass rises 125%
Plasma volume rises 150%
So [Hb] falls
By which trimester is dilution of plasma volume complete?
2nd trimester
What is the most common cause of anaemia in pregnancy?
Physiological rather than a deficiency
Why do you get macrocytosis in pregnancy?
Could be because of vitamin B12/folate deficiency
What change occurs in the neutrophil count in pregnancy?
You get a neutrophilia
**think of it as an imflammatory process**
How do platelets change in pregnancy?
Increase in size (but decrease in number)
Because of increased turnover–>increased number of immature platelets released into the circulation
What is the foetal and maternal requirement of iron in pregnancy?
300mg to foetus
500mg to mother for increased RBC production
Differentials of micrcocytic anaemia in pregnancy
- IDA
- Thalassaemia trait (haemoglobinopathy)
What is the RDA of iron in pregnancy?
30mg
Why is iron deficiency risky during pregnancy?
Risk of IUGR, post partum haemorrhage, prematurity
When do you consider iron supplementation in pregnancy?
What supplements exist and for how long do you need to take them?
If ferritin <30 ug/L
Supplements:
a) Ferrous sulphate
b) Pregaday
c) Pregnacare
**must continue for 3 months following correction of Hb
When is the folic acid supplement recommended in pregnancy?
400 ug (300ug more than normal): Before conception until 12 weeks gestation
What are the cutoffs for anaemia in each trimester of pregnancy?
1: <110g/l
2: <105g/l
3: <100g/l
*so Hb falls as you go through the pregnancy
What are the most important differentials in microcytic anaemia in pregnancy to consider?
IDA
Thalassaemia trait
What might cause thrombocytopaenia in pregnancy?
- Mostly gestational (physiological) thrombocytopaenia
- Pre-eclampsia (often causes DIC)
- Immune thrompocytopaenia (ITP) - this can be unmasked by pregnancy (but would be present already)
*difficult to distinguish b/w physiological and ITP*
- Microangiopathic syndromes
- All other causes: bone marrow failure, leukaemia, hyperplenism, DIC etc.
What platelet count is necessary for a woman to have spinal anaesthesia when giving birth?
>70x10^9/l
Below this there is a risk of spinal haematoma formation
WHat is the mechanism of physioogical trhombocytopaenia in pregnancy?
Unknown but could be because of
a) Dilution
b) Increased activation and consumption of platelets
**platelet count returns to normal day 2-5 after delivery
What is the mechanism of microangiopathic thrombocytopaenia in pregnancy?
Deposition of platelet rich thrombi within teh blood vessels
As the platelets are within the clots they don’t get counted in the blood count
Examples of microangiopathic syndromes in pregnancy
TTP
HUS
Pre-eclampsia
HELPP syndrome
Give 2 options for ITP treatment in pregnancy
IV immunoglobin
Steroids/azothioprine to immunosuppress
In which type of thrombocytopaenia in pregnancy can the baby be affected?
ITP
This is because IgG can cross the placenta
What is the key feature of MAHA?
Deposition of platelet-rich clots in blood vessels (rather than fibrin-rich)
What will be seen on a blood film of someone with MAHA?
Shistocytes (red cell fragments)
Mechanism of thrombocytopaenia in pre-eclampsia
How is DIC in pregnancy different to DIC otherwise?
In normal DIC you get prolonged PT/APTT because clotting factors are used up
IN pregnancy DIC- because clotting factors actually increase, you don’t get prolonged PT/APTT.
**thrombocytopaenia may be the only sign of DIC
Why do you get prothrombotic state even though you have low platelets in pregnancy?
Because of the low quality of platelets- they are actually more likely to clot
Which causes of thrombocytopaenia in pregnancy DO NOT RESOLVE after delivery?
TTP and HUS
All others i.e. gestational thrombocytoapenia, ITP and pre-eclampsia will resolve after delivery
How does platelet count change post-delivery in gestational thrombocytopaenia vs ITP?
GT: increases 3-5 days post-delivery
ITP: remits after delivery
What factors cause pro-coagulable state in pregnancy?
All elements of virchow’s triad are altered in pregnancy
a) Vessel wall injury- due to oestrogen
b) Hypercoagulable state- clotting factors increase, clotting inhibitors decrease
c) Stasis- decreased venous return to the heart
When is risk of venous thromboembolism most likely in pregnancy?
6 weeks after pregnancy
Where is venous thromboembolism most common in pregnancy?
Left leg
Is venous thromboembolism more likely in vaginal birth or C section?
C section
More likely in emergency c-section than elective c-section
What is the leading cause of mortality in pregnancy?
Venous thromboembolism
What are the main changes to clotting factors during pregnancy?
Why does pregnancy cause a hypofibrinolytic state?
Increase in PAI-2
PAI inhibits Urokinase and Tissue Plasminogen Activator which both promote fibrolysis
Therefore more PAI –> less fibrinolysis
How do you investigate VTE in pregnancy?
Dopplers are the safest
Why do you not do a D-dimer in pregnancy when there is suspected VTE?
Because it will be raised anyway
**weirdly, D-dimer is raised in pregnancy despite pregnancy being a hypofibrinolytic state
Which anti-coagulant should never be used in pregnancy?
Warfarin (cross the placenta)
What are the risk factors for VTE in pregnancy?
- gestation- most common 6 weeks post delivery
- increaeed maternal age
- parity
- multiple pregnancy
- obesity
- hyperemesis gravidarum
- ovarian hyperstimulation syndrome
- delivery method- operative delivery higher risk
- family history/personal history
- air travel
VTE prophylaxis in pregnancy
treatment of thromboembolic disease in pregnancy
Complications of thrombophilia in pregnancy
How does APLS present in pregnancy? How is it treated?
Post-partum. haemorrhage
>500ml blood loss
RF: tone, tissue, trauma, thrombin
**mostly caused by uterine atony
*see O&G
Pregnancy and DIC
Pregnancy preidposes to DIC
DIC is precipitated by:
a) amniotic fluid embolism
b) missed miscarriage
c) placental abruption
d) severe pre-eclampsia
What is amniotic fluid embolism? When does it presesent?
Happens when tissue factor goes from amniotic fluid to the maternal blood and triggers DIC.
Usually happens in third trimester
Risk is increaeed with labour inducing drugs
What is the point of haemoglobinopathy screening?
To identify alpha and beta zero thalassaemia, sickle cell and other compound syndromes (eg SC sickle cell anaemia)
Which thalasseamia cannot be identified by HPLC?
Alpha 0 thalassaemia
Needs molecular diagnosis via DNA analysis
When do you see pencil cells?
Iron deficiency anaemia
How do you distinguish between HELPP syndrome and DIC?
HELPP syndrome: normal APTT and PT
DIC: increased APTT and PT
summarise the main changes in haematology in pregnancy
When does ITP happen compared to gestational thrombocytopaenia?
ITP- first trimester
Gestational thrombodytopaenia- 3rd trimester
