Thrombocytopenia in pregnancy

Definition

• Thrombocytopenia in pregnancy is defined as a platelet count below 150,000/µl; it occurs in 7–12% of pregnancies.

Classification

• It is mild at counts above 100,000/µl and moderate at 50,000–100,000/µl.
• By cause, obstetric forms such as gestational thrombocytopenia and pre-eclampsia are distinguished from systemic disorders such as immune thrombocytopenia (ITP) and thrombotic thrombocytopenic purpura.

Occurrence & epidemiology

Epidemiology

• It is the second most common haematological abnormality of pregnancy.

Aetiopathogenesis

Aetiology and pathogenesis

• Gestational thrombocytopenia accounts for 75–80% of all cases, making it the most common cause, and probably results from haemodilution and accelerated platelet clearance.
• In ITP, maternal IgG antiplatelet antibodies cross the placenta and can cause fetal and neonatal thrombocytopenia.

Clinical features

Clinical features and complications

• Gestational thrombocytopenia mostly occurs in the mid-to-late second or the third trimester and is not associated with neonatal thrombocytopenia.
• Typical features are mucosal bleeding such as epistaxis and gingival bleeding, as well as petechiae and ecchymoses; life-threatening bleeding is infrequent.

Diagnosis

• Full blood count and blood smear serve to exclude pseudothrombocytopenia due to EDTA-induced platelet clumping.
• ITP typically presents before pregnancy or in the first trimester and is a diagnosis of exclusion.
• In thrombotic microangiopathy, schistocytes on the blood smear, raised bilirubin and LDH and decreased haptoglobin are found.

Keep learning in the app

Further reading (selection)

1. Rev Bras Ginecol Obstet 2020: Update on Thrombocytopenia in Pregnancy (PubMed Central)
2. StatPearls: Thrombocytopenia in Pregnancy (NCBI Bookshelf)

Cross-references