Do you start aspirin (acetylsalicylic acid) in pregnancy for thrombocytosis (high platelets)?

Management of High Platelets (Thrombocytosis) in Pregnancy

Aspirin should be initiated for pregnant women with essential thrombocythemia (ET) who are JAK2 mutation positive or have cardiovascular risk factors, but should be avoided in cases of extreme thrombocytosis with acquired von Willebrand syndrome or bleeding events. 1

Risk Assessment and Treatment Algorithm

For Essential Thrombocythemia (ET):

• Aspirin is recommended for ET patients who are JAK2 mutation positive or have cardiovascular risk factors 1
• Observation alone is reasonable if the patient is JAK2 unmutated or has extreme thrombocytosis (platelet count >1,000/μL) 1
• For extreme thrombocytosis (>1,000/μL), test for acquired von Willebrand syndrome (AvWS) with ristocetin co-factor and multimer analysis 1
• If extreme thrombocytosis persists during pregnancy with AvWS or bleeding events, aspirin should be avoided 1

For Polycythemia Vera (PV):

• Aspirin plus phlebotomies to maintain hematocrit <45% is recommended 1
• Cytoreductive therapy with interferon-alpha (IFN-α) is indicated for high-risk patients with prior thrombosis history 1

For Reactive Thrombocytosis:

• Reactive thrombocytosis (even with platelet counts >1,000/μL) has not been shown to cause thrombosis 2
• Focus on treating the underlying condition rather than the platelet count itself 2

Special Considerations

High-Risk Patients:

• Consider IFN-α therapy in low-risk patients with:
  • History of poorly controlled hematocrit levels
  • Prominent splenomegaly
  • Recurrent fetal loss 1

Peripartum Management:

• Hold aspirin for 3 days prior to delivery in patients with extreme thrombocytosis to reduce bleeding risks associated with neuraxial anesthesia 1
• Resume aspirin postpartum for appropriate patients 1
• Monitor blood counts for 4-6 weeks postpartum as VTE risk is highest during this period 1

Safety Profile of Aspirin in Pregnancy

• A meta-analysis of 31 randomized studies in pregnant women at risk for preeclampsia showed that aspirin therapy was not associated with increased risk of pregnancy loss, neonatal hemorrhage, or growth restriction 1
• Low-dose aspirin (<100 mg/day) has not been associated with significant effects on neonatal platelet function 1
• Aspirin crosses the placenta, and some studies have suggested a possible association with gastroschisis when used in the first trimester, though the validity of this risk estimate is questionable 1

Common Pitfalls to Avoid

• Do not use aspirin in patients with extreme thrombocytosis and acquired von Willebrand syndrome as it may increase bleeding risk 1
• Avoid hydroxyurea and warfarin during pregnancy as they are teratogenic 1
• Do not use direct oral anticoagulants (dabigatran, rivaroxaban, apixaban) during pregnancy 1
• Remember that aspirin should be held for 3 days prior to delivery in patients with extreme thrombocytosis 1

Evidence Strength and Limitations

• The recommendation for aspirin use in ET during pregnancy is based on expert consensus rather than large randomized controlled trials 1
• The benefit of aspirin for primary thromboprophylaxis in ET is partially extrapolated from studies in polycythemia vera, which may not be directly applicable 2
• A small study of pregnant women receiving low-dose aspirin (40 mg/day) with dipyridamole showed inhibition of platelet aggregation without clinically significant bleeding 3

In summary, the decision to start aspirin in pregnancy with high platelets depends on the underlying cause of thrombocytosis and associated risk factors. For essential thrombocythemia, aspirin is recommended if JAK2 mutation is positive or cardiovascular risk factors are present, but should be avoided with extreme thrombocytosis and acquired von Willebrand syndrome.