What is the workup for thrombocytopenia (low platelet count) in the postpartum period?

Workup for Thrombocytopenia in Postpartum Period

The workup for postpartum thrombocytopenia should include a thorough evaluation of potential causes, with special attention to distinguishing between gestational thrombocytopenia, immune thrombocytopenia (ITP), and other pregnancy-specific conditions, as these have different implications for maternal and neonatal outcomes. 1, 2

Initial Assessment

• Document any bleeding symptoms including bruising, petechiae, and menorrhagia 2
• Review complete blood count trends, focusing on platelet count values and trends over time 2
• Obtain comprehensive medical history, including:
  • Previous history of thrombocytopenia when not pregnant (suggests ITP rather than gestational thrombocytopenia) 3
  • Timing of onset of thrombocytopenia (first appearing in late gestation suggests gestational thrombocytopenia) 3
  • Severity of thrombocytopenia (counts typically >70,000 in gestational thrombocytopenia) 3
  • Medication history and family history of bleeding disorders 2

Laboratory Evaluation

• Complete blood count with peripheral smear examination to exclude other causes of thrombocytopenia 3
• Coagulation studies including PT, INR, aPTT, and fibrinogen 2
• Blood pressure measurement to rule out preeclampsia as an alternative diagnosis 3
• Liver function tests to exclude HELLP syndrome 3
• HIV antibody testing for patients with risk factors 3
• Consider testing for other secondary causes of thrombocytopenia (HCV, H. pylori) 2

Differential Diagnosis Considerations

• Gestational thrombocytopenia (most common cause, accounting for ~75% of cases):

  • Typically mild (platelet count >70,000)
  • Occurs during late gestation
  • No previous history of thrombocytopenia except possibly during previous pregnancies
  • Resolves spontaneously after delivery
  • Not associated with fetal thrombocytopenia 3

• Immune thrombocytopenia (ITP):

  • May have history of thrombocytopenia when not pregnant
  • Can occur at any time during pregnancy
  • May be associated with neonatal thrombocytopenia 3

• Pregnancy-specific conditions:

  • Preeclampsia/HELLP syndrome (evaluate blood pressure, liver function) 3
  • Acute fatty liver of pregnancy 4

• Other causes:

  • Thrombotic thrombocytopenic purpura (consider ADAMTS13 testing) 4
  • Hemolytic uremic syndrome 4
  • Drug-induced thrombocytopenia 5

Management Considerations

• Monitoring of platelet count trends is essential, with increased frequency as postpartum period progresses 1
• For mild thrombocytopenia (platelet count >50,000) without bleeding symptoms, observation alone may be sufficient 3
• Be aware that even mild thrombocytopenia (100,000-149,000) is associated with a twofold greater likelihood of postpartum hemorrhage compared to normal platelet counts 6
• Treatment is required for women with platelet counts <10,000, and for those with platelet counts of 10,000-30,000 who are bleeding 3

Neonatal Considerations

• Cord blood platelet count should be determined after delivery by clean venipuncture of a cord vessel 3
• Infants with subnormal counts should be observed clinically and hematologically, as platelet counts tend to nadir between days 2-5 after birth 3
• Transcranial ultrasonography should be performed on neonates with platelet counts <50,000/μL 3, 2
• For neonates with clinical hemorrhage or platelet counts <20,000/μL, treatment with IVIg 1 g/kg may be indicated 3

Common Pitfalls and Caveats

• Fetal or neonatal platelet count cannot be reliably predicted by maternal platelet count, platelet antibody levels, or history of maternal splenectomy for ITP 3
• Attempts to measure fetal platelet count before delivery (cordocentesis or scalp sampling) are not recommended due to associated risks 3
• Gestational thrombocytopenia and ITP cannot be distinguished with certainty during pregnancy as both diagnoses are based on exclusion of other causes 3
• Even mild thrombocytopenia in the postpartum period warrants close monitoring due to increased risk of postpartum hemorrhage 6