29 Jul

Use of Antithrombotic Agents During Pregnancy: Summary and Conclusions

Anticoagulant therapy is indicated during pregnancy for the prevention and treatment of VTE, for the prevention and treatment of systemic embolism in patients with mechanical heart valves, and, in combination with aspirin, for the prevention of pregnancy loss in women with APLA and previous pregnancy losses. Several questions concerning anticoagulant therapy remain unanswered. Oral anticoagulants are fetopathic, but the tme risks of the warfarin embryopathy and CNS abnormalities are unknown. There is some evidence that warfarin embryopathy occurs only when oral anticoagulants are administered between the 6th and the 12th weeks of gestation and that oral anticoagulants may not be fetopathic when administered in the first 6 weeks of gestation. Oral anticoagulant therapy should be avoided in the weeks before delivery because of die risk of serious perinatal bleeding caused by the trauma of deliveiy to the anticoagulated fetus. The safety of aspirin during the first trimester of pregnancy is still a subject of debate. Canadian neighborhood pharmacy itat on There is a concern about the efficacy of unfractionated heparin in the prevention of arterial embolism in pregnant women with mechanical heart valves. Finally, the role of LMWH and heparinoids and appropriate dosing have still to he determined.
Because it is safe for the fetus, heparin is the anticoagulant of choice during pregnancy for situations in which its efficacy is established. The evidence for the efficacy of heparin for the prevention and treatment of VTE disorders during pregnancy is based on level IV studies. There is some doubt that heparin is effective for the prevention of systemic embolism in patients with mechanical heart valves. Low doses of heparin or poorly controlled heparin therapy are not effective in preventing systemic embolism in patients with mechanical heart valves.
Table 1—Recommendations

Condition Recommendation Grading of Recommendation
Previous venous thrombosis or PE prior to current pregnancy Heparin (5,000 U ql2h or adjusted to produce a heparin level of 0.1-0.2 U/mL) throughout pregnancy followed by warfarin postpartum for 4 to 6 weeks C2
orClinical surveillance followed by warfarin postpartum for 4 to 6weeks C2
orLMWH C2
Venous thrombosis or PE during current pregnancy Heparin in full IV doses for 5-10 days, followed by ql2h subcutaneous injections to prolong 6-h postinjection APTT into the therapeutic range until delivery; warfarin can then be used postpartum Cl
Planning pregnancy in patients who are being treated with long-term oral anticoagulants Either heparin ql2h subcutaneously to prolong 6-h postinjection APTT into the therapeutic range C2
orFrequent pregnancy tests and substitute heparin (as above) for warfarin when pregnancy achieved C2
Mechanical heart valves Either heparin ql2h subcutaneously to prolong 6-h postinjection APTT into the therapeutic range C2
orAdjusted-dose subcutaneous heparin until the 13th week, warfarin (target I NR of 3.0 [range 2.5-3.5]) until the middle of the third trimester,* then adjusted-dose subcutaneous heparin until delivery C2
APLA and > 1 previous pregnancy loss Aspirin plus heparin A1
APLA and previous venous thrombosis Heparin ql2h subcutaneously to prolong 6-h postinjection APTT into the therapeutic range C2
APLA without previous venous thrombosis Either clinical surveillance C2
orHeparin 5,000 U ql2h throughout pregnancy

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