Venous thromboembolism in pregnancy and the puerperal period: a study of 1210 events.

OBJECTIVE: The aim of this study was to describe venous thromboembolism (VTE) in pregnancy and the puerperal period, and to validate diagnoses of VTE.

DESIGN: Historical cohort study.

POPULATION: All pregnancies in Denmark from 1995 to 2009.

METHODS: VTE diagnoses were retrieved from national registries.

MAIN OUTCOME MEASURES: Positive predictive value of a VTE diagnoses diagnosed during pregnancy or the puerperal period. Location of VTE. Incidence rate of confirmed, validated diagnoses of VTE and on all retrieved diagnoses of VTE.

RESULTS: In 1 297 037 pregnancies, 1436 women had a first-ever VTE diagnosis. Hospital records were retrieved for 1210 women (84.3%). Almost all women had relevant clinical symptoms and in 796 (65.8%), the diagnosis were confirmed by a positive diagnostic test or by instituted anticoagulation treatment. In all, 72.6, 53.7, 58.5 and 79.1% of the diagnoses were confirmed in the first, second, third trimester and the puerperal period, respectively. The 796 cases of VTE included 624 women with deep venous thrombosis only and 133 with pulmonary embolisms. Deep venous thrombosis was located in the left lower limb in 83.8% in pregnancy, compared with 67.9% in the puerperal period.

CONCLUSIONS: The vast majority of women with a registered diagnosis of VTE had relevant symptoms. Diagnoses of VTE were confirmed in the medical records in two of three women. VTE diagnoses were most often confirmed when made in the first trimester and in the puerperal period. Left-sided deep venous thrombosis was the predominant type of VTE in pregnancy and the puerperal period.