Prevention of Venous Thromboembolism (VTE) Associated with Pregnancy in Women with a Past History of VTE.

Abstract 3132

Poster Board III-69

Women with a past history of venous thrombosis are at higher risk for venous thromboembolism (VTE) during and after pregnancy. The highest risk period is the first four weeks post partum. For a woman whose previous event was secondary to a major transient risk factor the antepartum risk of recurrent VTE is low whereas for women whose previous event was idiopathic the antepartum risk is higher. In our institution, for women whose previous event was secondary to a major transient risk factor, standard treatment is to follow closely with no thromboprophylaxis antepartum and then receive either prophylactic low molecular weight heparin (LMWH) or warfarin for six weeks postpartum. For women whose previous event was idiopathic or who were on warfarin at the time of becoming pregnant they receive prophylactic LMWH antepartum with a scheduled delivery and are put back on warfarin if they have long term anticoagulation needs or LMWH for six weeks if they don't have longterm anticoagulation needs. We report the outcome for our patients from 1997 to 2008. All patients were followed for the duration of pregnancy and for 6 weeks postpartum for pregnancy outcome, recurrent VTE, and major bleeding in the thrombosis clinic of London Health Sciences Centre. There were a total of 90 women; 30 women (mean age 30.6 years) with a history of previous secondary thrombosis with 37 pregnancies and 60 women (mean age 29.5 years) with past idiopathic thrombosis with 99 pregnancies. For the secondary group there was 1 episode (2.70%; 95% CI 0.48-13.82) of antepartum recurrent VTE whereas for the idiopathic group there were 3 episodes (3.03%; 95% CI 1.04-8.53). There was no statistical difference between groups (p=1.0). There were no episodes of postpartum VTE recurrence or major hemorrhage for either group. For the secondary group there was 1 fetal loss at 23 weeks (2.7%; 95% CI 0.48-13.82) whereas for the idiopathic group there were 6 fetal losses at 8, 10, 10, 11, 22, 37 weeks gestation (6.06%; 95% CI 2.81-12.60). There was no statistically significant difference between groups (p=0.77). This retrospective review suggests that for pregnant women with a past history of VTE, a strategy of no antepartum prophylaxis for previous secondary thrombosis and antepartum prophylactic LMWH for previous idiopathic thrombosis as well as prophylactic LMWH or warfarin postpartum is efficacious and safe.