Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study

J Thromb Haemost. 2008 Apr;6(4):632-7. doi: 10.1111/j.1538-7836.2008.02921.x. Epub 2008 Jan 31.


Background: Venous thrombosis is one of the leading causes of maternal morbidity and mortality.

Objective: In the MEGA study, we evaluated pregnancy and the postpartum period as risk factors for venous thrombosis in 285 patients and 857 control subjects.

Patients/methods: Between March 1999 and September 2004, consecutive patients with a first episode of venous thrombosis were included from six anticoagulation clinics. Partners of patients and a random digit dialing group were included as control subjects. Participants completed a questionnaire and DNA was collected.

Results: The risk of venous thrombosis was 5-fold (OR, 4.6; 95% CI, 2.7-7.8) increased during pregnancy and 60-fold (OR, 60.1; 95% CI, 26.5-135.9) increased during the first 3 months after delivery compared with non-pregnant women. A 14-fold increased risk of deep venous thrombosis of the leg was found compared with a 6-fold increased risk of pulmonary embolism. The risk was highest in the third trimester of pregnancy (OR, 8.8; 95% CI, 4.5-17.3) and during the first 6 weeks after delivery (OR, 84.0; 95% CI, 31.7-222.6). The risk of pregnancy-associated venous thrombosis was 52-fold increased in factor V Leiden carriers (OR, 52.2; 95% CI, 12.4-219.5) and 31-fold increased in carriers of the prothrombin 20210A mutation (OR, 30.7; 95% CI, 4.6-203.6) compared with non-pregnant women without the mutation.

Conclusion: We found an increased risk of venous thrombosis during pregnancy and the postpartum period, with an especially high risk during the first 6 weeks postpartum. The risk of pregnancy-associated venous thrombosis was highly increased in carriers of factor V Leiden or the prothrombin 20210A mutation.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / genetics
  • Activated Protein C Resistance / epidemiology
  • Activated Protein C Resistance / genetics
  • Adult
  • Case-Control Studies
  • DNA Mutational Analysis
  • Factor V / genetics
  • Female
  • Humans
  • Middle Aged
  • Netherlands
  • Pregnancy
  • Pregnancy Complications, Hematologic / epidemiology*
  • Pregnancy Complications, Hematologic / etiology
  • Pregnancy Trimesters
  • Prothrombin / genetics
  • Puerperal Disorders / epidemiology*
  • Puerperal Disorders / etiology
  • Pulmonary Embolism / epidemiology
  • Pulmonary Embolism / etiology
  • Risk
  • Risk Factors
  • Surveys and Questionnaires
  • Thrombophilia / etiology
  • Thrombophilia / genetics
  • Thrombophlebitis / epidemiology
  • Thrombophlebitis / etiology
  • Venous Thrombosis / epidemiology*
  • Venous Thrombosis / etiology


  • 3' Untranslated Regions
  • factor V Leiden
  • Factor V
  • Prothrombin