How is thrombocytopenia (low platelet count) managed in a pregnant patient?

Management of Thrombocytopenia in Pregnancy

Treatment is indicated only when platelet counts fall below 20,000-30,000/μL in asymptomatic pregnant women, or at any platelet count if there is active bleeding. 1, 2

Diagnostic Evaluation

The first step is excluding pregnancy-specific causes before diagnosing immune thrombocytopenic purpura (ITP):

• Measure blood pressure and obtain liver function tests to rule out preeclampsia, HELLP syndrome, acute fatty liver of pregnancy, and DIC 1, 2
• Do not perform bone marrow examination as it is not required for ITP diagnosis in pregnancy 1
• Do not order antiplatelet antibody testing as it has no diagnostic value 1
• Exclude gestational thrombocytopenia, folate deficiency, massive obstetrical hemorrhage, and antiphospholipid antibody syndrome 1

Treatment Thresholds by Clinical Scenario

Observation Only

• Platelet counts >50,000/μL throughout pregnancy require no treatment 2
• Platelet counts of 30,000-50,000/μL without bleeding can be observed in first and second trimesters 1

Treatment Required

• Counts <10,000/μL at any gestational age mandate treatment 2
• Counts 10,000-30,000/μL with active bleeding require treatment regardless of trimester 2
• Counts <20,000-30,000/μL even if asymptomatic warrant treatment 1

First-Line Treatment Options

Prednisone 10-20 mg/day is the initial treatment of choice, adjusted to the minimum dose that maintains hemostatic platelet counts 1, 2

IVIg is used when:

• Corticosteroids are ineffective or cause significant side effects 1
• Rapid platelet increase is required 1
• Patient is in third trimester with counts <10,000/μL or 10,000-30,000/μL with bleeding 2

Second-Line Options for Refractory Cases

• IV anti-D 50-75 μg/kg for non-splenectomized Rh(D)-positive patients in second and third trimesters, usually requiring augmentation with corticosteroids or IVIg to reach target of 50,000/μL 1
• High-dose methylprednisolone (1000 mg) possibly combined with IVIg or azathioprine 1
• Azathioprine is safe during pregnancy based on SLE and transplant data, though response is slow 1
• Cyclosporin A has not been associated with significant maternal or fetal toxicity 1
• Splenectomy is best performed in second trimester if necessary, may be done laparoscopically but is technically difficult beyond 20 weeks 1

Management at Delivery

Target Platelet Counts

• ≥50,000/μL for safe vaginal delivery or cesarean section 3
• ≥75,000/μL if neuraxial anesthesia is desired to minimize epidural hematoma risk 3

Mode of Delivery

The mode of delivery should be determined by obstetric indications alone, not by maternal platelet count 1, 2—there is no evidence that cesarean section is safer for the thrombocytopenic fetus than uncomplicated vaginal delivery 1

Prophylactic Platelet Transfusions

Transfuse platelets before delivery when:

• Maternal platelets <10,000/μL with planned cesarean section 1, 2
• Epistaxis or mucous membrane bleeding with expected vaginal delivery 1, 2

Regional Anesthesia Considerations

• No changes to routine practice are required until platelet count drops below 50,000/μL when INR, aPTT, and fibrinogen are normal and there is no bruising, bleeding history, or anticoagulation 4
• For counts below 50,000/μL, careful risk-benefit analysis is needed with multidisciplinary discussion 4
• Spinal may be safer than epidural blockade due to smaller needle size and decreased risk of vascular damage 4
• Monitor the trend as well as absolute value—rapidly falling counts require closer observation than stable low counts 4

Procedures to Avoid During Labor

Do not use the following due to increased fetal hemorrhagic risk: 4

• Fetal scalp electrodes
• Fetal blood samples
• Ventouse delivery
• Rotational forceps
• Cordocentesis for fetal blood sampling (carries 1-2% fetal mortality risk) 1

Neonatal Management

Monitoring

• Check cord blood platelet count at delivery by clean venepuncture of cord vessel, not by draining blood from cord 4
• Monitor neonatal platelet counts for 3-4 days after birth as counts typically nadir at 24-48 hours (days 2-5) after delivery 4, 2, 3
• Avoid intramuscular injections (including vitamin K) until platelet count is known 4

Neonatal Treatment Indications

• IVIg 1 g/kg for neonatal platelets <20,000/μL without evidence of intracranial hemorrhage 4, 2
• Treat clinical hemorrhage regardless of platelet count 4
• Life-threatening hemorrhage requires platelet transfusion combined with IVIg 4

Imaging

• Perform transcranial ultrasonography on neonates with platelet counts <50,000/μL at delivery 4
• Consider brain imaging if platelet count at birth is <20,000/μL 1

Critical Pitfalls to Avoid

• Fetal or neonatal platelet count cannot be reliably predicted by maternal platelet count, platelet antibody levels, or history of maternal splenectomy 1
• Most neonatal hemorrhagic events occur 24-48 hours after delivery at the platelet nadir, not during delivery itself 1
• Severe neonatal thrombocytopenia and clinical hemorrhage are rare (neonatal mortality <1%, intracranial hemorrhage 0-1.5%) 1
• When severe neonatal thrombocytopenia and hemorrhage are present, exclude neonatal alloimmune thrombocytopenia by laboratory testing 4
• Neonatal thrombocytopenia secondary to maternal ITP may last for months and occasionally requires a second dose of IVIg at 4-6 weeks after birth 4

Special Considerations

Venous Thromboembolism

Despite thrombocytopenia, ITP in pregnancy may be associated with a prothrombotic state due to anticardiolipin antibody syndromes or other pregnancy-related factors, and VTE prophylaxis should be considered 4

Subsequent Pregnancies

In ITP, the second fetus is usually as affected as the first (unlike alloimmune thrombocytopenia where fetal thrombocytopenia tends to worsen in subsequent pregnancies) 4