Gestational Thrombocytopenia

Gestational thrombocytopenia is a mild, benign fall in platelets during the second or third trimester, with a normal count before pregnancy and recovery within 1 to 2 months after delivery.

It is caused by haemodilution and increased platelet turnover.

It matters because it needs no treatment and must be separated from preeclampsia and immune thrombocytopenia.

Platelet count is usually 100 to 150 x 10^9/L, rarely down to 70 x 10^9/L.

Not associated with bleeding or fetal thrombocytopenia.

It may recur in later pregnancies.

Women have no symptoms, no bleeding and a normal examination, with the low count found on routine blood tests. Blood pressure, urine and liver tests are normal.

No history of low platelets before pregnancy.

No petechiae or purpura.

The diagnosis is by exclusion in a well woman with a mild late fall in platelets.

• Platelet count 100 to 150 x 10^9/L (rarely 70 to 100) on repeat testing; film to exclude clumping and fragments.
• Normal blood pressure, urine protein, liver enzymes, lactate dehydrogenase, creatinine and coagulation screen.
• HIV, hepatitis B and C tests, malaria test; antiphospholipid antibodies if there is a history of miscarriage or thrombosis.
• Normal count before pregnancy and recovery after delivery confirm the diagnosis.

The principle is observation, with repeat counts and safe delivery, and no drug treatment.

• Supportive: reassure; routine antenatal and delivery care; avoid aspirin and NSAIDs if platelets fall below 50 x 10^9/L; inform the anaesthetist of the count.
• Pharmacological: none needed; paracetamol 1 g oral 6-hourly as needed (maximum 4 g in 24 hours) for pain; oxytocin 10 IU IM at delivery.
• Procedures: none; vaginal delivery is expected, and epidural anaesthesia is acceptable if the platelet count is above 70 x 10^9/L and stable.
• Red flags: platelets falling below 70 x 10^9/L, bleeding, blood pressure above 140/90 mmHg, headache, upper abdominal pain, jaundice.
• Follow-up: repeat platelet count every 2 to 4 weeks, weekly after 36 weeks and at delivery; repeat count at 6 weeks postpartum; if still low, evaluate for immune thrombocytopenia.