Haematology 9 - Obstetric haematology Flashcards by Adya Rao

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

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By which trimester is dilution of plasma volume complete?

2nd trimester

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What is the most common cause of anaemia in pregnancy?

Physiological rather than a deficiency

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Why do you get macrocytosis in pregnancy?

Could be because of vitamin B12/folate deficiency

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What change occurs in the neutrophil count in pregnancy?

You get a neutrophilia

**think of it as an imflammatory process**

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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

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What is the foetal and maternal requirement of iron in pregnancy?

300mg to foetus

500mg to mother for increased RBC production

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Differentials of micrcocytic anaemia in pregnancy

IDA
Thalassaemia trait (haemoglobinopathy)

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What is the RDA of iron in pregnancy?

30mg

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Why is iron deficiency risky during pregnancy?

Risk of IUGR, post partum haemorrhage, prematurity

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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

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When is the folic acid supplement recommended in pregnancy?

400 ug (300ug more than normal): Before conception until 12 weeks gestation

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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

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What are the most important differentials in microcytic anaemia in pregnancy to consider?

IDA
Thalassaemia trait

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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.

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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

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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

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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

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Examples of microangiopathic syndromes in pregnancy

TTP

HUS

Pre-eclampsia

HELPP syndrome

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Give 2 options for ITP treatment in pregnancy

IV immunoglobin

Steroids/azothioprine to immunosuppress

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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?

1. gestation- most common 6 weeks post delivery 2. increaeed maternal age 3. parity 4. multiple pregnancy 5. obesity 6. hyperemesis gravidarum 7. ovarian hyperstimulation syndrome 8. delivery method- operative delivery higher risk 9. family history/personal history 10. 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