thrombocytopenia of pregnancy (gestational thrombocytopenia)

Etiology

• incidental thrombocytopenia of pregnancy (gestational thrombocytopenia) most common
• thrombotic microangiopathy of pregnancy (see Differential diagnosis below)

Epidemiology

• 10% of women with uncomplicated pregnancies

Pathology

• platelet counts of 100,000-150,000/uL are typically caused by gestational thrombocytopenia, a normal physiologic process involving expanded intravascular volume & splenic as well as placental sequestration of platelets
• platelet counts < 100,000/uL may be due to pathology such as ITP, preeclampsia, or HELLP syndrome

Clinical manifestations

• presentation during 2nd & 3rd trimester

Laboratory

• defined as platelet count < 150,000/uL at delivery
• complete blood count
  • thrombocytopenia, platelet count > 70,000/uL
  • platelet count < 50,000/uL (< 70,000/uL) suggests ITP
• peripheral blood smear: no shistocytes

Differential diagnosis

• platelet counts < 100,000/uL
  • immune thrombocytopenic purpura (ITP)
    • platelet count < 50,000/uL (< 70,000/uL)
    • 1st trimester
    • prior history of thrombocytopenia
  • thrombotic microangiopathy of pregnancy
    • preeclampsia
      • hypertension, proteinuria, edema, > 20 weeks gestation
    • HELLP syndrome:
      • hemolysis, abnormal liver function tests, > 20 weeks gestation
    • thrombotic thrombocytopenic purpura/hemolytic uremic syndrome
      • > 20 weeks gestation, not affected by termination of pregnancy
    • acute fatty liver of pregnancy
      • hypoglycemia, coagulopathy at > 20 weeks of gestation
    • disseminated intravascular coagulation (DIC)

Management

• no treatment is required for platelet counts > 50,000/uL (> 100,000/uL)
• for platelet counts < 50,000/uL see ITP, HELLP syndrome
• goal of pregnant patients with ITP is a platelet count > 30,000-40,000 until the end of the 3rd trimester when a platelet count > 50,000/uL is needed for a safe delivery
  • platelet count > 80,000/uL if spinal anesthesia anticipated
• treat with immune globulin or glucocorticoids
• immediate delivery of fetus with thrombotic microangiopathy of pregnancy

More general terms

• pregnancy disorder; obstetric disorder; pregnancy complication
• thrombocytopenia