Use of Antithrombotic Agents During Pregnancy: Anticoagulant Therapy During Pregnancy
Thus, retrospective studies have reported the incidence of recurrent VTE to be as high as 15% during pregnancy in women with previous deep-vein thrombosis (DVT). In contrast, the results of one randomized trial reported that 1 of 20 untreated patients (5%) with previous VTE developed recurrent antepartum VTE, and a cohort study (published in letter form) reported that none of 59 pregnant patients with previous VTE developed antepartum recurrence. It is likely that the risks of both initial and recurrent DVT are higher postpartum than antepartum. Conclusions from all of these studies are limited by their relatively small numbers and lack of descriptions of the inception cohorts. Controlled clinical trials are required to establish the true incidence of recurrent VTE in pregnant women, and the safety and efficacy of anticoagulant therapy in preventing recurrent VTE.
Anticoagulant Therapy During Pregnancy
The agents currently available for the prevention and treatment of VTE include heparin and heparin-like compounds (unfractionated heparin, LMWH, and hepari-noids) and coumarin derivatives.
Fetal Complications of Anticoagulants During Pregnancy
There are two potential fetal complications of maternal anticoagulant therapy: teratogenicity and bleeding. Canadian health and care mall more Heparin does not cross the placenta, and therefore does not have the potential to cause fetal bleeding or teratogenicity, although bleeding at the uteroplacental junction is possible. Two studies strongly suggest that heparin therapy is safe for the fetus.
In contrast to heparin, coumarin derivatives cross the placenta and have the potential to cause both bleeding in the fetus and teratogenicity. Coumarin derivatives can cause an embryopathy, which consists of nasal hypoplasia and/or stippled epiphyses after in utero exposure to oral anticoagulants during the first trimester of pregnancy, and CNS abnormalities, which can occur after exposure to such drugs during any trimester. It is possible that oral anticoagulants are safe during the first 6 weeks of gestation, but there is a risk of embryopathy if coumarin derivatives are taken between 6 and 12 weeks of gestation. In addition, these oral anticoagulants cause an anticoagulant effect in the fetus that is a concern, particularly at the time of delivery, when the combination of the anticoagulant effect and trauma of delivery can lead to bleeding in the neonate.