New blood clot guidelines for pregnant women

New evidence-based guidelines address the prevention and management of thrombosis in key patient populations and reinforce recommendations related to the routine use of preventive therapies. Published as a supplement in the June issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians (ACCP), Antithrombotic and Thrombolytic Therapy: ACCP Evidence-Based Clinical Practice Guidelines, Eighth Edition was developed by an international panel of 90 experts and includes more than 700 of the most comprehensive recommendations related to the prevention, treatment, and long-term management of thrombotic disorders. The guidelines include chapters on the challenges in preventing and treating thrombosis in pregnant women and children, and on managing peri- and postoperative patients, while also reinforcing previous guidelines related to the routine use of preventive therapies, including aspirin.

"For years, clinicians have faced challenges in preventing and managing thrombosis in women who are pregnant or patients who require surgery," said guidelines panel chair Jack Hirsh, MD, FCCP, Henderson Research Center, Hamilton, ON, Canada. "The new guidelines address many troublesome issues in antithrombotic therapy and provide clinicians with a variety of options for care in special patient groups." Antithrombotic and thrombolytic therapies are used to prevent and treat thrombosis or blood clotting that arises in arteries, veins, and the heart.

PREGNANT WOMEN

The new ACCP guidelines address challenging issues facing women who are pregnant or wish to become pregnant while undergoing long-term antithrombotic therapy. Pregnant women taking vitamin K antagonists (VKA), such as the anticoagulant warfarin, have an increased risk for birth defects and miscarriage and are, therefore, advised to stop taking VKAs before 6 weeks of fetal gestation. However, some pregnant women with certain types of mechanical heart valves may be continued on VKA therapy because of concerns about the effectiveness of alternative anticoagulants in preventing stroke and valve thrombosis. For other women taking VKAs who become pregnant, the guidelines recommend substituting low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH). The guidelines recommend two options for doing this: (1) continuing VKA but performing frequent pregnancy tests to determine when pregnancy has been achieved, followed by the substituion of LMWH or UFH as therapy; or (2) substituting VKAs with LMWH or UFH prior to conception. Although the second option eliminates the potential for fetal exposure to VKA, it provides additional challenges. LMWH and UFH are more expensive than VKAs and must be administered through a once- or twice-daily injection as opposed to a once daily oral dose of VKAs. In addition, long-term use of LMWH or UFH can be associated with osteoporosis.

"If women substitute heparin prior to pregnancy and have difficulties conceiving, they may find themselves taking the medication for a much longer timeframe than expected," said guideline coauthor Shannon Bates, MD, McMaster University and Henderson Research Centre, Hamilton, Ontario, Canada. "This is not only inconvenient but also increases treatment costs and may be associated with long-term risks for the mother."