[CG] Thrombocytopenia in pregnancy

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Definition

The normal serum level of platelets in pregnancy is 120–400 x 109/l. 

Reduction of serum platelet count is considered; 

Mild    >100-120 x 109/l
Moderate 50–100 x 109/l
Severe  <50 x 109/l  

 

Symptoms

Common symptoms of thrombocytopenia include petechiae, epistaxis and more rarely, haematuria and gastrointestinal bleeding. Symptoms are uncommon above a count of 50 x 109/l  

Causes

  • Spurious result
  • Gestational thrombocytopenia
  • Immune thrombocytopenia (ITP)
  • Pre- eclampsia and HELLP (Haemolysis, Elevated LFTs, Low Platelets) syndrome
  • Disseminated Intravascular Coagulation (DIC)
  • Haemolytic Uraemic Syndrome (HUS)
  • Thrombotic Thrombocytopenic Purpura (TTP)
  • HIV, Hep C and other infections
  • Drugs
  • Systemic Lupus Erythematosus (SLE)
  • Antiphospholipid syndrome (ALPS)
  • Bone marrow disease e.g. congenital platelet disorder, leukaemia, lymphoma

Incidence

  • 8-10% pregnant women at term have thrombocytopenia
  • 75% of these have gestational thrombocytopenia
    • No clinical implications
    • Normal platelet count out with pregnancy
    • Late onset, usually third trimester
    • Count < 70 is unusual
    • Platelet count returns to normal within 2-12 weeks postpartum
  • 21% cases due to pre-eclampsia, associated with;
    • Raised BP, proteinuria
    • Deranged LFTs, U&Es, haemolysis
  • 4% cases due to Immune Thrombocytopenia
    • 2/3 ITP cases already known
    • Can have significant thrombocytopenia in first trimester
    • Diagnosis of exclusion
  • Miscellaneous causes in the remaining 1% cases e.g. HUS, TTP etc

Evaluation of thrombocytopenia in pregnancy

Exclude medical disorders and drug induced thrombocytopenia

  • Blood Film (mandatory)
    • Platelet clumping – repeat in citrate / lithium heparin
    • Microangiopathic haemolytic anaemia – HELLP/TTP/HUS/DIC
  • LFTs, U&Es, Urates, coagulation screen, HIV, Hep C
  • If all negative, the diagnosis of exclusion is either gestational thrombocytopenia or ITP

Management

  • Isolated mild thrombocytopaenia (120-150) confirmed – no additional monitoring required
  • Isolated moderate/severe thrombocytopenia confirmed – monitor platelet count
    • Monthly in 1st and 2nd trimester
    • Fortnightly in 3rd trimester
    • Weekly from 36 weeks

Note: Frequency of monitoring depends on severity 

  • Platelet count should be checked on admission to the labour ward
  • Platelet antibody testing is unhelpful and does not predict fetal / neonatal thrombocytopenia
  • Bone marrow aspirate is not required (unless haematological malignancy suspected)
  • Liaise with anaesthetist when platelet count <100x109/l
  • Liaise with haematologist when platelet count <70x109/l
  • Treat when platelet count is below the intervention level
  • If there is development of significant bleeding symptoms, a target platelet count of >50x109/l should be aimed for

Intervention levels for non-haemorrhagic thrombocytopenia

Intervention

Platelet count(x109/l)

Antenatal, no invasive procedures planned

Vaginal delivery

Operative or instrumental delivery

Epidural anaesthesia

<20

<40

<50

<100

The remainder of this guideline refers to the management of cases of ITP in pregnancy. Other causes of thrombocytopenia should be managed according to their underlying pathology.

Management of ITP     

Maternal considerations

Most women only require treatment for delivery. Usually either oral corticosteroids or IV immunoglobulins are used

  • Oral Corticosteroids
    • Response in 2-3 weeks
    • Use lowest effective dose for shortest time
    • Start with 20mg/day of prednisolone until a response is obtained. Assess response on a weekly basis.
    • Increase dose to 1mg/kg/day if no or minimal response at one week
    • Following an initial response, wean the dose to the lowest that maintains a platelet count above intervention level
    • Disadvantages – glucose intolerance, hypertension, psychosis, osteoporosis
  • IV gamma globulin
    • Response in 24-48 hrs (lasts 2-3 weeks)
    • Dosage: 0.4g/kg/day for 5 days or 1g/kg for 2 days, repeated after 48 hrs if there is no response
    • Disadvantages - slow infusion, plasma product, allergic reactions, headache, less commonly aseptic meningitis, rarely renal toxicity
  • Platelet transfusions are given as a last resort for bleeding or prior to surgery along with IVIG and tranexamic acid
  • IV anti D has lost its license for treatment of ITP
  • Intravenous methylprednisolone may be considered in patients who fail to respond to oral prednisolone and/or immunoglobulins
  • Rituximab and azathioprine are effective but should only be considered in resistant cases
  • Splenectomy should be avoided in pregnancy but may become necessary in extreme cases. If so, it should be performed in the 2nd trimester. Penicillin prophylaxis should be continued post splenectomy and vaccinations should be given post partum

 

Fetal Considerations

Babies born to mothers suffering from ITP may have a low platelet count. Maternal platelet count co-relates poorly with neonatal platelet count.

Predictors for neonatal thrombocytopenia are

  • Previously affected sibling (Neonatal alloimmune thrombocytopenia {NAIT} should be considered in these cases, maternal platelet count is usually normal in NAIT)
  • Previous splenectomy
  • Severe ITP

5% of babies have a platelet count between 20-50 x 109/l

5% have a platelet count <20 x 109/l 

Intracranial haemorrhage is rare (<1% cases)

Fetal scalp electrode, fetal blood sampling, ventouse and complicated forceps delivery should be avoided

Caesarean section is reserved for obstetric indications only

 

Assessment of the newborn

  • All babies should have a cord blood sample taken
    • Normal FBC – no further samples required
    • Below normal FBC – neonatal FBC sample must be taken
    • Below normal neonatal sample – alternate day FBC for one week as nadir usually occurs at day 3-5 of life
  • Treatment
    • Platelets >20 x 109/l – Monitor. Oral vitamin K if <50 x 109/l
    • Platelets <20 x 109/l – IVIG + cranial USS + oral vitamin K (and consider NAIT as an alternative diagnosis)
    • Life threatening bleeding – IVIG + platelet transfusion (consider transfusion of HPA 1a 5b negative platelets until NAIT is excluded)
  • Thrombocytopenia may take from a few weeks to occasionally months to resolve
References

Catherine Nelson-Piercy. Thrombocytopenia, Haematological problems, Handbook of obstetric medicine, third edition.

Provan D. et al., International consensus report on the investigation and management of primary immune thrombocytopenia. Blood. 2010;115:168-186

Myers B. Thrombocytopenia in pregnancy. The Obstetrician & Gynaecologist 2009;11:177– 183.

Last reviewed: 28 May 2016

Next review: 30 June 2021

Author(s): Catherine Bagot, Andrew Thomson

Version: 2

Approved By: Approved on behalf of GGC Obstetric Guidelines Group by Dr Fiona Mackenzie, Consultant Obstetrician, PRM