Use of Antithrombotic Agents During Pregnancy: Recommendations
Previous Venous Thromboembolism (Prophylaxis)
In pregnant women with a history of previous venous thromboembolic disease, the true risk of recurrence in untreated patients is unknown and estimates range from 0 to 15%.~ Consequently, some form of prophylaxis or surveillance should be considered. Our approach is to use clinical surveillance antepartum (widr postpartum warfarin) in women whose previous VTE was secondary to a transient risk factor. In those with previous idiopathic VTE or thrombophilia with no previous VTE, we recommend either clinical surveillance or low-dose heparin (either 5,000 U ql2h subcutaneously or adjusted to produce a heparin level of 0.1 to 0.2 U/mL) throughout pregnancy Click Here canadian family pharmacy. Finally, in those with previous venous thrombosis and thrombophilia, we favor adjusted-dose subcutaneous heparin. With all options, heparin and warfarin should then be used postpartum for 4 to 6 weeks. These are grade C2 recommendations (Table 1).
Treatment of Venous Thromboembolism of Pregnancy
In patients who develop venous thrombosis during pregnancy, full doses of heparin should be given by IV infusion for 5 to 10 days and then by subcutaneous injection ql2h in full doses until term. This recommendation is based on a level I study of nonpregnant patients, and on a level IV study of pregnant patients that reported the efficacy of heparin for the treatment of acute venous thrombosis. Heparin should be discontinued immediately before delivery and then both heparin and warfarin can be started postpartum. Once a therapeutic INR is obtained, heparin can be discontinued and warfarin administered for a further 4 to 6 weeks. This is a grade Cl recommendation.
Unexpected Pregnancy or Planned Pregnancy in Patients Who Are Being Treated With Long-term Anticoagulant Therapy
Patients receiving long-term oral anticoagulant therapy for venous thromboembolism or patients with mechanical heart valves present problems when planning pregnancy or if pregnancy occurs unexpectedly. It is possible that oral anticoagulants are safe during the first 6 weeks of gestation, but there is a risk of warfarin embryopathy if warfarin is taken between 6 and 12 weeks of gestation. Ideally, such women should be counselled before pregnancy occurs. If anticoagulant therapy is indicated during pregnancy, the risks should be explained before conception. If pregnancy is still desired, two options can be considered. The first is to perform frequent pregnancy tests and to substitute heparin for warfarin when pregnancy is achieved. The second is to replace warfarin with heparin before conception is attempted. Both approaches have limitations; the first assumes that warfarin is safe during the first 4 to 6 weeks of gestation and the second increases the duration of exposure to heparin and, therefore, to a higher risk of osteoporosis. We favor the first approach because it is convenient and appears to be safe. These are grade C2 recommendations.