Related Experiment Video
Updated: Jul 7, 2026

Disruption of the Mouse Blood-Brain Barrier by Small Extracellular Vesicles from Hypoxic Human Placentas
Published on: January 26, 2024
Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study
E R Pomp1, A M Lenselink, F R Rosendaal
1Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
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.
Related Concept Videos
Venous Thrombosis I: Introduction
Mitral Valve Prolapse III: Nursing Management
Venous Thrombosis II: Clinical Manifestations and Diagnostic Studies
Venous Thrombosis III: Interprofessional Care
Venous Thrombosis IV: Nursing Management
Pulmonary Embolism I: Introduction