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Anticoagulation for Patients with Mechanical Heart Valves During Pregnancy Survey
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Anticoagulation for Patients with Mechanical Heart Valves during Pregnancy: A Survey


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Description Abstract:

Patients with mechanical heart valves (MHVs) require life-long anticoagulation to prevent thromboembolic complications (TEs). The risk of TEs is increased during pregnancy and women with MHVs have only a 58% chance of experiencing an uncomplicated pregnancy with a live birth. Non-pregnant women with MHVs are treated with vitamin-K antagonists (VKAs) e.g warfarin, but as VKAs traverse the placenta and are teratogenic, alternative anticoagulation regimens have been used in pregnancy with the aim of reducing fetal risks. There is a need to optimize anticoagulant therapy antepartum in patients with mechanical heart valves as these women are at increased risk of thrombosis and bleeding and exposure to teratogenic drugs, the vitamin K antagonists e.g. warfarin. There are 3 options for anticoagulation during pregnancy for these women, low molecular weight heparin (LMWH) throughout pregnancy, VKAs throughout pregnancy, LMWH in the first trimester and VKAs in the second and third trimester. The risk of VKA induced embryopathy (predominantly midfacial hypoplasia and stippled epiphyses) is between 3-6% during 6-12 weeks gestation. At any time during pregnancy VKAs are associated with an increased risk of CNS abnormalities, dorsal or midline ventral dysplasia but these are rare occurrences (fetopathy).  Approximately 1% of women develop thrombosis of prosthetic mechanical valves with VKAs and 3% develop thromboembolic complications.

If LMWH is substituted for VKAs between 6 to 12 weeks, as LMWH does not traverse the placenta, there is no risk of embryopathy but there remains a risk of fetopathy as VKAs would be restarted after 12 weeks gestation. The rate of thrombosis of the prosthetic mechanical valve also increases and is 5% and thromboembolic complications 6%.

If LMWH during the entire antenatal period, there is no risk of embryopathy or fetopathy but  the rate for thrombosis of the mechanical valve and thromboembolic complications increases to 10% and 10% respectively. 


Principal Investigator: Drs. Maha Othman, Patricia Casais,  Nadine Shehata, and Isabelle Malhame

Collaborators: Dr. Isabelle Malhalme, Brown’s University,  Candice Silversides, Division of Cardiology, Department of Medicine University of Toronto,  Dr. Rohan D’Souza, Maternal Fetal Medicine Physician, Department of Obstetrics and Gynecology, University of Toronto, Dr. Rachel Wald, Division of Cardiology, Department of Medicine, University of Toronto, Dr. Mathew Sermer, Maternal Fetal Medicine Physician, Department of Obstetrics and Gynecology, University of Toronto, Special Pregnancy Program, Mount Sinai Hospital




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