Thrombocytopenia in pregnancy

From IDWiki

Background

Definition

  • Low platelet count in pregnancy, generally considered to be less than 100

Pathophysiology

  • Most commonly, thrombocytopenia of pregnancy is caused by dilution from increased plasma volume, similar to anemia in pregnancy, and is usually more noticeable in T2 and T3

Etiology

Epidemiology

  • About 10% of pregnant women have platelets less than 150

Clinical Manifestations

Disease % Diagnostic Features Lab Findings Clinical Features Pathophys Comments
Gestational thrombocytopenia 5-9 Onset 2nd-3rd trimester. Normal PLT previously. No neonatal thrombocytopenia. Plt >70 Typically normal Unclear Diagnosis of exclusion. Resolves postpartum. No fetal thrombocytopenia.
ITP <1 Onset any trimester. May see thrombocytopenia outside pregnancy. Plt <100 +/- large platelets May have bleeding, bruising, petechiae Antibody-mediated peripheral plt destruction with decrease thrombopoiesis. Diagnosis of exclusion. May be associated with fetal thrombocytopenia.
Preeclampsia 5-8 Onset late 2nd or 3rd trimester (>20 weeks). Proteinuria >0.3 g/d BP ≥140/90 Systemic endothelial dysfunction. Inadequate placentation. May precede other manifestations of preeclampsia. Can present postpartum.
HELLP <1 70% late 2nd or 3rd trimester, 30% postpartum. MAHA, high liver enzymes, high LDH. Signs of preeclampsia, but may be normotensive without proteinuria. Same as preeclampsia. Variant of preeclampsia.
AFLP <0.01 Onset in 3rd trimester. Plt >50. High liver panel, creat, WBC, urate, ammonia. High PT/PTT, decreased fibrinogen. Hypoglycemia. RUQ pain. Jaundice, nausea/vomiting. Hepatic encephalopathy. Preeclampsia spectrum. MAHA not characteristic. Conjugated bili often high. Liver dysfunction greater than HELLP/preeclampsia.
TTP/aHUS <0.01 Onset any trimester, but more common during 3rd or postpartum. MAHA, elevated creatinine, schostocytes on blood film. Fever, abdo pain, n/v, headache, vis changes, altered mental status. Congenital deficiency of ADAMTS13 (TTP) or complement dysregulation (aHUS). ADAMTS13 activity <5% in TTP. Liver panel and BP usually normal.


Investigations

  • CBC and blood film
    • Look for bicytopenia concerning for thrombotic microangiopathy
    • Platelets <70 more consistent with ITP than gestational thrombocytopenia
  • For ITP
    • HIV, HBV, HCV
    • Liver and thyroid tests
    • Immunoglobulin levels
    • DAT
    • APLA and ANA
  • Platelet antibody testing is useless

Management

  • Depends on etiology
  • Gestational thrombocytopenia
    • No specific management
  • ITP
    • No need to treat until 36 weeks if platelets over 30
    • If platelets < 30 or bleeding
      • Prednisone (0.25-1 mg/kg) or IVIg (1 g/kg ideally body weight, max 60mg)
    • Monitor newborn for post-partum thrombocytopenia

Prognosis

  • In ITP, 25% of neonates will have thrombocytopenia and 10% will need treatment