Disorder | Onset during pregnancy | Diagnosis |
Pseudothrombocytopenia | Any time | Examine blood smear for platelet clumps, or giant platelets. Repeat platelet count in citrate or heparin anticoagulant. Usually caused by agglutinins dependent upon EDTA, the standard anticoagulant for blood counts. |
Gestational thrombocytopenia (GT) | Typically late in gestation, frequency increases as term approaches | Based on five criteria:
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Immune thrombocytopenia (ITP) | Any time | Presence of isolated thrombocytopenia with no evidence for alternative etiologies. May be indistinguishable from gestational thrombocytopenia if mild and occurs late during pregnancy. Platelet count may improve after delivery. |
Preeclampsia with severe features | After 20 weeks gestation | Systolic or diastolic hypertension plus proteinuria |
HELLP syndrome (hemolysis, elevated liver function tests, and low platelets) | After 20 weeks gestation | Diagnostic criteria for preeclampsia are present in 85% of cases. Hemolysis: Microangiopathic hemolytic anemia with schistocytes, with other signs of hemolysis: increased serum LDH and indirect bilirubin, decreased haptoglobin Elevated liver function tests (eg, AST, ALT), typically ≥twice normal Low platelets: Platelet count ≤100,000/microL |
Thrombotic thrombocytopenic purpura (TTP) | Typically late in gestation, frequency increases as term approaches. May occur after delivery. | Thrombocytopenia and microangiopathic hemolytic anemia without an alternative etiology. May be indistinguishable from severe preeclampsia or HELLP syndrome. Severe neurologic abnormalities and acute renal failure support the diagnosis of TTP. Persistent abnormalities ≥3 days after delivery also support the diagnosis of TTP. |
Drug-induced immune thrombocytopenia (DITP) (except heparin) | Any time | Complete history of drug ingestion, including non-prescription drugs and herbal remedies. Focus on drugs taken intermittently, or regularly for more than one week. Thrombocytopenia typically resolves in five to seven days after stopping the drug. |
Heparin-induced thrombocytopenia (HIT) | Any time | Suspected in patients who have thrombocytopenia (or >50% decrease in platelet count) and who have begun heparin within previous 5 to 10 days. Thrombocytopenia is typically mild; arterial or venous thrombi are commonly present. ELISA assay for heparin-dependent antibodies is sensitive; measurement of heparin-induced platelet serotonin release is more specific. |
Antiphospholipid syndrome (APS) | Any time | Requires one clinical and one laboratory criterion: Clinical:
Laboratory: Demonstration of the persistent presence of at least one of the following antiphospholipid antibodies:
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