Thrombocytopenia is a common finding which occurs in 7-12% of pregnant women. The cause of isolated thrombocytopenia may be differentiated by history, physical examination, laboratory investigation, and medical imaging.

CLINICAL ACTIONS:

When evaluating a patient for gestational thrombocytopenia (GT), consider the following

• Use platelet count <150 x 10⁹/L to define thrombocytopenia in pregnancy
  • Normal platelet range in nonpregnant women is 165-415 x 10⁹/L
  • Expect lower platelet counts in pregnant women, especially 3^rd trimester
• Order the following tests to assist with diagnosis/underlying cause
  • complete blood count and peripheral smear
  • liver enzymes
  • thyroid function tests
  • vitamin B12 and folate
  • HCV,HIV,HBV
  • pT/pTT
  • antinuclear antibody, anticardiolipin antibodies, lupus inhibitor
  • Based on clinical context, may require medical imaging to evaluate splenic size
• Diagnose GT in the absence of historical, clinical, hematological and biochemical findings that would suggest another underlying condition
• Transfuse platelets to achieve minimum platelet counts
  • >10 x 10⁹/L without surgery/procedures
  • >50 x 10⁹/L before major surgery
  • >80 x 10⁹/L prior to epidural

SYNOPSIS:

GT is the most common cause of thrombocytopenia in pregnancy and accounts for 80% of such cases.  GT may be a result of hemodilution and enhanced platelet clearance. The low platelet counts associated with GT are seen during the second and third trimesters with the nadir rarely lower than 70 x 10⁹/L. The diagnosis of GT is made by the presence of a decreased platelet count during pregnancy and should be considered a diagnosis of exclusion. GT usually resolves within days to two months postpartum.

KEY POINTS:

Primary immune thrombocytopenia (ITP) may be difficult to distinguish from GT

• ITP induces development of platelet autoantibodies that may cross the placenta
• Features that may help distinguish GT from ITP
  • GT usually mid-late 2^nd & 3^rd trimester / ITP all trimesters
  • GT only in pregnancy / ITP may occur outside pregnancy
  • GT will resolve postpartum / ITP may not resolve
  • GT does not affect fetus or neonate / ITP may cause neonatal thrombocytopenia
• If the diagnosis thrombocytopenia is unclear at the time of delivery, assume ITP and manage accordingly due to fetal/newborn risk for thrombocytopenia
  • Mode of delivery in ITP should be based on obstetric indications alone
• ITP treatment options comparable to non-pregnant management – corticosteroids and intravenous immune globulin (IVIG)
  • In pregnancy, may start at lower end of prednisone dose (10-20 mg daily) and titrate up
• Both GT and ITP may recur

Other disorders resulting in non-isolated thrombocytopenia that will present with other related findings include

• Primary thrombotic microangiopathies (TMA)
  • ADAMTS13-deficient TMA – Thrombotic thrombocytopenic purpura (TTP)
  • Complement-mediated TMA – Atypical hemolytic uremic syndrome
• Preeclampsia
  • 50% of women with preeclampsia will have <150 x 10⁹/L
  • HELLP syndrome
• Disseminated intravascular coagulation (DIC)
  • Severe preeclampsia
  • Intrauterine fetal demise (IUFD)
  • HELLP syndrome
  • Acute fatty liver of pregnancy
• Infection (e.g., HIV, hepatitis C, CMV, Helicobacter pylori)
• Drug induced (e.g. heparin, antimicrobials, anticonvulsants)

Learn More – Primary Sources:

Thrombocytopenic syndromes in pregnancy

ACOG Practice Bulletin 166: Thrombocytopenia in Pregnancy

Locate a Maternal Fetal Medicine Specialist:

Maternal Fetal Medicine Specialist Locator-SMFM

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