Thrombocytopenia in Pregnancy (ASH 2013)

Intro

Definition of thrombocytopenia in preganancy: Plt Count <100 x109/L (International Working Group)

2nd most common haematologic abnormality in pregnancy, after anaemia

6-11% of women have plt count <150 in third trimester

 

Haematologist’s role:

  • Determine the cause, advise on management, estimate risk to mother and fetus

 

Common Scenarios

1. Pre-existing thrombocytopenia

2. Decreasing platelet count or newly discovered thrombocytopenia in pregnancy, which may or may not be related to the pregnancy

3. Acute onset thrombocytopenia in the setting of severe pre-eclampsia, HELLP or AFLP

 

Causes (% relative incidence)

 

Isolated thrombocytopenia

Gestational Thrombocytopenia (70-80%)

Primary ITP  (1-4%)

Secondary ITP -Hep C, HIV, H. pylori (1%)

Drug-induced

Type IIb VWD

Congenital thrombocytopenias

 

Thrombocytopenia associated with systemic disorders

Severe pre-eclampsia (15-20%)

HELLP (<1%)

AFLP (<1%)

TTP / aHUS

SLE

Antiphospholipid Syndrome

Viral infections

Nutritional deficiency

Splenic sequestration (liver disease, portal vein thrombosis)

Thyroid disorders

 

Basic Investigations

 

FBC, reticulocyte count, blood film

LFTs

Viral Screening

 

Also consider if indicated:

  • ANA, TFT, H. pylori, PT/APTT/FGN, DAT, Immunoglobulins

 

Gestational Thrombocytopenia

 

Platelet Count >70 + No neonatal thrombocytopenia + spontaneous maternal resolution

 

5-9% of pregnancies, 70-80% of all thrombocytopenias in pregnancy

 

Timing

Occurs in mid-second to third trimester

Resolves within 6 weeks post-partum, may recur with subsequent pregnancies

Not associated with neonatal thrombocytopenia

 

Mechanism

Unknown, ?dilution + accelerated clearance

 

Management of Mother

Exclude other causes

If plt count <70, question diagnosis

Repeat FBC 6 weeks post-partum

 

Management of baby

If suspicious, Cord FBC and repeat at day 4 to exclude ITP

 

Immune Thrombocytopenia (ITP)

 

Platelet Count <100 +/- symptoms

 

Timing

Onset at any time

 

Steroids

Initial response: 2-14 days

Peak response: 4-28 days

Prednisolone preferred to dexamethasone (which crosses placenta)

Dose

  • ASH 2011 recommend 1mg/kg prednisolone

  • But other experts recommend 0.25-0.5mg/kg and titrate to effect

 

IVIg

Initial response: 1-3 days

Peak response: 2-7 days

Dose: 1g/kg

 

Other treatments

Splenectomy

Relatively contra-indicated: Anti-D Ig, Azathioprine

Not recommended, but case resports: Cyclosporin, Dapsone, TPO agonists, Rituximab

Contraindicated: MMF, Cyclophosphamide, Vinka alkaloids, Danazol

 

ITP Pregnancy Management Plan

 

Antenatal

Plt count >30 and no bleeding symptoms

No treatment until 36 weeks, or sooner if early delivery

Plt count <30 or clinically significant bleeding

First line: Prednisolone 0.25 - 1mg/kg or IVIg 1g/kg

Second line: Combination treatment or splenectomy

Delivery

Mode of delivery determined by obstetric indications

Very low risk of ICH (<1.5%) or mortality (<1%)

Targets

Platelet count >50 prior to labour as C-section is a risk with any pregnancy

Platelet count >80 required for neuroaxial anaesthesia

 

Plt count <80 but not required treatment during pregnancy

Start 10-20mg prednisolone 10 days prior to expected delivery and titrate

 

Plt count <50 and delivery is imminent

Platelet transfusion combined with IVIg

 

Fetus/Neonate

No scalp monitoring / percutaneous umbilical cord blood sampling (PUBS)

Cord blood FBC & hold Vit K until result known

If cord FBC normal, Repeat FBC at day 4

Expect spontaneous rise above nadir by day 7

Consider cranial USS if plt <50. Consider single dose IVIg if plt <20 or bleeding

 

Postparum

Increased risk of VTE, ensure prophylaxis arranged

 

Severe Pre-Eclampsia / HELLP / AFLP

 

Severe Pre-eclampsia

Pre-eclampsia affects 5-8% of pregnancies

  • Sys >140 or Dys >90 + >0.3g/24 hour proteinuria after 20 wks gestation

Severe pre-clampsia

  • Several different criteria, one of which is plt count <100

  • Thrombocytopenia may precede the other manifestations

  • Can present postpartum

 

Haemolysis, Elevated Liver enzymes and Low Platelets (HELLP)

Variant of pre-eclampsia, in some cases HTN and Proteinuria not present

70% in late second to third trimester, 30% postpartum

MAHA + Raised AST + Thrombocytopenia

 

Acute Fatty Liver of Pregnancy (AFLP)

Plt count >50

Rare but serious condition of third trimester

Elevated liver enzymes, conjugated bilirubinaemia, coagulopathy

Overlaps with HELLP, differentiation not clearly defined but MAHA unusual

 

Obstetric Management of Severe Pre-Elcampsia/HELLP/AFP

IV magnesium to prevent seizures, Anti-hypertensives for BP

>34 weeks

  • Delivery

<34 weeks and maternal/fetal status acceptable

  • Steroids for lung maturation and deliver after 48 hours

<34 weeks and maternal/fetal status unacceptable

  • Delivery

 

Haematology Management

Supportive care with platelet transfusion

Steroids increase plt count but do not improve outcomes

Plasma exchange if plt, haemolysis or renal failure no better 48-72 hours after delivery

 

TTP / aHUS

 

Difficult to differentiate severe pre-eclampsia, HELLP, AFLP, TTP and aHUS

  • TTP: ADAMTS13 <5%

When indicated, therapeutic plasma exchange is beneficial in all of these conditions and so diagnostic certainty not required in emergency setting.

See MAHA & TTP section