ABO blood groups and risk of venous thromboembolism during pregnancy and the puerperium. A population-based, nested case-control study

J Thromb Haemost. 2005 Feb;3(2):300-4. doi: 10.1111/j.1538-7836.2005.01195.x.


Objectives: To examine possible associations of ABO blood types with the risk of venous thromboembolism (VTE) in pregnancy and the puerperium.

Patients and methods: We conducted a nested case-control study within a cohort of 71,729 women who gave birth to 126,783 children in the North Jutland County, Denmark, from 1980 to 2001. We identified 129 cases with VTE in pregnancy (n = 61) or the puerperium (n = 68), and 258 controls with no VTE. We collected information on ABO blood groups and possible maternal confounding factors and estimated the relative risk [odds ratio (OR)].

Results: Women with an A or AB blood group had elevated risk estimates of VTE in pregnancy or the puerperium compared with women with a O blood group [adjusted ORs 2.4, 95% confidence interval (CI) 1.3, 4.3, and 2.0, 95% CI 0.7, 5.8, respectively]. No increased risk estimate was found for group B (adjusted OR 1.2, 95% CI 0.5, 3.0). The increased risk estimates of VTE for blood groups A and AB appeared present in both pregnancy (adjusted ORs of 3.9, 95% CI 1.5, 9.7, and 2.2, 95% CI 0.4, 12.5) and in the puerperium (adjusted ORs of 2.4, 95% CI 1.0, 4.9 and 2.7, 95% CI 0.8, 9.3). Furthermore, blood groups A and AB appeared to be associated with increased risk estimates for both DVT and pulmonary embolism.

Conclusion: Keeping the modest statistical precision of our study in mind, blood groups A and AB may be associated with increased risk estimates for VTE in pregnancy and the puerperium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ABO Blood-Group System / physiology*
  • Adult
  • Case-Control Studies
  • Female
  • Humans
  • Odds Ratio
  • Postpartum Period / blood*
  • Predictive Value of Tests*
  • Pregnancy
  • Pregnancy Complications, Cardiovascular / blood
  • Pregnancy Complications, Cardiovascular / epidemiology
  • Pregnancy Complications, Cardiovascular / etiology*
  • Risk Assessment
  • Thromboembolism / blood
  • Thromboembolism / epidemiology
  • Thromboembolism / etiology
  • Venous Thrombosis / blood
  • Venous Thrombosis / epidemiology
  • Venous Thrombosis / etiology*


  • ABO Blood-Group System