Venous thromboembolism during pregnancy or postpartum: findings from the RIETE Registry.

Venous thromboembolism (VTE) occurs infrequently during pregnancy, and issues concerning its natural history, prevention and therapy remain unresolved. RIETE is an ongoing registry of consecutive patients with objectively confirmed, symptomatic acute VTE. In this analysis, we compared the clinical characteristics and outcome for all enrolled pregnant and postpartum women with acute VTE, and all non-pregnant women in the same age range. Up to May 2005, 11,630 patients were enrolled in RIETE, of whom 848 (7.3%) were women aged <47 years. Of them, 72 (8.5%) were pregnant, 64 (7.5%) postpartum. Pregnant women presented less often with symptomatic pulmonary embolism (11%) than non-pregnant women (39%). VTE developed during the first trimester in 29 (40%) pregnant patients; in the second in 13; in the third in 30. Thrombophilia tests were more often positive in women who had VTE during the first trimester (odds ratio [OR]: 4.4; 95% CI: 0.9-2.4; p=0.037). Most patients in all three groups were initially treated with low-molecular-weight heparin (LMWH). As for long-term therapy, 75% of pregnant women received LMWH until delivery. There were no maternal deaths, and no pregnant patient had recurrence or bled before delivery. However, after delivery one patient (1.4%) developed recurrent thrombosis, four (5.6%) had major bleeding. In conclusion, VTE developed during the first trimester in 40% of the pregnant women, thus suggesting that thromboprophylaxis, when indicated during pregnancy, should start in the first trimester. No patient showed recurrence or bled before delivery, but after delivery the risk of bleeding exceeded the risk of recurrences.