Thrombocytopenia in Pregnancy: Causes and Diagnostic Considerations

Primary Causes by Frequency

Gestational thrombocytopenia accounts for approximately 75% of all cases of thrombocytopenia in pregnancy, characterized by asymptomatic, mild thrombocytopenia, and occurs during late gestation, with platelet counts typically remaining >70,000/μL 1, 2, 4
Hypertensive disorders of pregnancy, including preeclampsia and HELLP syndrome, account for approximately 20-25% of cases, and predominantly occur in the third trimester 1, 2, 6
Immune thrombocytopenia (ITP) is relatively uncommon, estimated to occur in 1 in 1,000 to 1 in 10,000 pregnant women, and is characterized by a history of thrombocytopenia when not pregnant, and may occur early in the first or second trimester 1, 4, 5

The American College of Obstetricians and Gynecologists recommends considering gestational thrombocytopenia, hypertensive disorders, and ITP in the differential diagnosis of thrombocytopenia in pregnancy 1, 2, 4
The timing of thrombocytopenia is crucial, with late-onset thrombocytopenia suggesting gestational thrombocytopenia or hypertensive disorders, and early-onset thrombocytopenia suggesting ITP or other pathology 4, 6
A thorough history is essential, with evidence of previous thrombocytopenia at a time when the patient was not pregnant strongly suggesting ITP rather than gestational thrombocytopenia 1, 2, 4

Antiphospholipid antibody syndrome should be considered in the differential diagnosis of thrombocytopenia in pregnancy 5
Folate deficiency may contribute to thrombocytopenia in pregnancy due to increased demands 5
Disseminated intravascular coagulation (DIC) is a critical diagnostic consideration, associated with septic abortion, amniotic fluid embolism, intrauterine fetal death, or massive obstetric hemorrhage 5, 7