Thrombocytopenia in Pregnancy

Thrombocytopenia in pregnancy is a platelet count below 150 x 10^9/L. Causes include gestational thrombocytopenia (the most common), preeclampsia and HELLP syndrome, immune thrombocytopenia, HIV, malaria, viral infection, antiphospholipid syndrome, thrombotic thrombocytopenic purpura and drugs. It matters because severe disease causes bleeding at delivery and some causes are life-threatening.

• Common in pregnancy.
• Platelet count above 100 x 10^9/L rarely causes problems.
• Finding the cause decides treatment.

Most women have no symptoms. Others have bruising, nosebleeds, gum bleeding, petechiae or heavy menstrual or vaginal bleeding. Check blood pressure, spleen, jaundice, fever and neurological signs.

• Petechiae and purpura suggest platelets below 30 x 10^9/L.
• Hypertension with proteinuria points to preeclampsia.
• Differential diagnosis: gestational thrombocytopenia, preeclampsia or HELLP syndrome, immune thrombocytopenia, HIV, malaria, thrombotic thrombocytopenic purpura, disseminated intravascular coagulation, antiphospholipid syndrome, systemic lupus erythematosus, drug induced thrombocytopenia, hypersplenism.
• Complications: bleeding, postpartum haemorrhage, spinal haematoma after neuraxial anaesthesia, neonatal thrombocytopenia (immune causes), intracranial haemorrhage.

The approach is repeat platelet count, film and a search for the cause.

• Repeat full blood count with a blood film to exclude platelet clumping (citrate tube if needed).
• Blood pressure, urine protein, liver enzymes, lactate dehydrogenase, bilirubin, creatinine, coagulation screen, fibrinogen.
• HIV test, hepatitis B and C, malaria test, antinuclear antibody, antiphospholipid antibodies, vitamin B12 and folate.
• Ultrasound for growth and spleen size; haemolysis film for fragmented cells.

The principle is to find the cause, treat it and keep platelets at safe levels for delivery.

• Supportive: avoid IM injections when platelets are below 50 x 10^9/L; avoid contact sports; avoid aspirin and NSAIDs when platelets are below 50 x 10^9/L; plan delivery in a facility with blood bank.
• Pharmacological: gestational thrombocytopenia needs none; immune thrombocytopenia: prednisolone 0.5 to 1 mg/kg oral daily (maximum 60 mg) for platelets below 30 x 10^9/L, with symptoms, or before delivery; immunoglobulin 1 g/kg IV daily for 1 to 2 days for platelets below 20 x 10^9/L with bleeding or before delivery; preeclampsia: labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine 10 to 20 mg oral 8-hourly, and magnesium sulphate 4 g IV over 20 minutes then 1 g per hour for 24 hours; HELLP syndrome: dexamethasone 10 mg IV 12-hourly for 2 doses; thrombotic thrombocytopenic purpura: plasma exchange 1 plasma volume daily with prednisolone 1 mg/kg oral daily; malaria: artesunate 2.4 mg/kg IV at 0, 12 and 24 hours then daily; platelet transfusion of 1 adult dose (apheresis unit or 4 to 6 pooled units) for platelets below 10 x 10^9/L, below 50 x 10^9/L for caesarean section or active bleeding, and below 30 x 10^9/L for vaginal delivery.
• Procedures: epidural anaesthesia is acceptable if platelets are above 70 x 10^9/L and stable; delivery is for obstetric reasons.
• Special groups: antiphospholipid syndrome uses aspirin 75 mg oral daily and enoxaparin 40 mg subcutaneous daily once platelets are above 50 x 10^9/L; neonates of women with immune thrombocytopenia have a cord platelet count and a count at 2 to 5 days.
• Red flags: platelets below 50 x 10^9/L, bleeding, blood pressure above 160/110 mmHg, jaundice, fever, confusion, haemolysis.
• Follow-up: platelet count every 2 to 4 weeks, weekly after 36 weeks and at delivery; repeat at 6 weeks postpartum; refer women with persistent low counts to a haematologist.