Prevalence and predictors for post-thrombotic syndrome 3 to 16 years after pregnancy-related venous thrombosis: a population-based, cross-sectional, case-control study.

BACKGROUND: The long-term outcome of pregnancy-related venous thrombosis (VT) is not known.

OBJECTIVES: To assess predictors and long-term frequency of post-thrombotic syndrome (PTS) after pregnancy-related VT.

PATIENTS/METHODS: In 2006, 313 women with pregnancy-related VT during 1990-2003 and 353 controls answered a comprehensive questionnaire that included self-reported Villalta score as a measure of PTS. Cases were identified from 18 Norwegian hospitals using the Norwegian Patient Registry and the Medical Birth Registry of Norway. The latter was used to select as possible controls women who gave birth at the same time as a case. Thirty-nine patients and four controls were excluded because of VT outside the lower limbs/lungs or missing Villalta scores. Two hundred and four patients had DVT in the lower limb and 70 had pulmonary embolism (PE). The control group comprised 349 women naive for VT at the time of the index pregnancy.

RESULTS: Forty-two per cent of cases with DVT in the lower limb, compared with 24% of cases with PE and 10% of controls, reported a Villalta score of ≥ 5. Severe PTS (Villalta score of ≥ 15) was reported among 7%, 4% and 1%. Proximal postnatal, but not antenatal, thrombosis was a strong predictor of PTS with an adjusted odds ratio of 6.3 (95% confidence interval, 2.0-19.8; P = 0.002). Daily smoking before the index pregnancy and age above 33 years at event were independent predictors for post-thrombotic syndrome.

CONCLUSIONS: PTS is a common long-term complication after pregnancy-related DVT. Proximal postnatal thrombosis, smoking and higher age were independent predictors of the development of PTS.