Recurrent venous thromboembolism and pregnancy

Current guidelines with respect to antepartum anticoagulation for women who have had a previous episode of venous thromboembolism (VTE) are not well defined, in part because the degree of risk has not been established in large clinical studies. Anticoagulation is recommended during the postpartum period for this patient group, since thrombotic risk is considered to be substantially increased. Pabinger and colleagues (page 1060) have addressed the risk for recurrent VTE during the antepartum period in a retrospective study of 109 women with a history of an episode of VTE who were followed for a total of 1014 years, of which 73 observation years occurred during pregnancy. The postpartum period was excluded for analysis, since anticoagulation during that time was recommended. In this study, 40% of the women tested positive for factor V Leiden and an additional 20% had another type of thrombophilia. In this group of 109 women, the recurrence rate of VTE in the antepartum period was 10.9 episodes per 100 patient years. Risk for recurrence was not necessarily based on the presence of thrombophilia.

Although not discussed in this paper, another reason to consider antepartum anticoagulation in women with thrombophilia is to reduce the likelihood of other complications such as pre-eclampsia, abruptio placentae, and fetal loss. The impact of anticoagulation on these adverse outcomes is unknown other than for women with the antiphospholipid syndrome.

The authors mention low molecular weight heparins (LMWHs) for prophylaxis; these agents are commonly used in pregnancy although not officially approved by the Food and Drug Administration in this clinical setting. Pabinger et al's study supports the need for a large, well-designed trial to define the risk-benefit ratio of antepartum anticoagulation, most likely with a LMWH, in women with and also without underlying thrombophilia who have had previous VTE.