Background: Lupus anticoagulant is an acquired antiphospholipid antibody that can increase greatly the risk of thromboembolism during pregnancy. Because a baseline elevated activated partial thromboplastin time (PTT) is associated frequently with this antibody, monitoring anticoagulant effect with activated PTT can be unreliable.
Case: A pregnant woman with lupus anticoagulant being treated with adjusted dose heparin experienced concurrent severe thrombotic and hemorrhagic complications.
Conclusion: This case illustrates the pitfall of activated PTT monitoring when administering anticoagulation therapy to a patient with a baseline elevated activated PTT. We propose that heparin levels be used to monitor anticoagulation in these patients.