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Duration and magnitude of the postoperative risk of venous thromboembolism in middle aged women: prospective cohort study

BMJ 2009; 339 doi: (Published 04 December 2009) Cite this as: BMJ 2009;339:b4583

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  1. Siân Sweetland, statistical epidemiologist1,
  2. Jane Green, clinical epidemiologist1,
  3. Bette Liu, senior research fellow14,
  4. Amy Berrington de González, investigator12,
  5. Marianne Canonico, research associate13,
  6. Gillian Reeves, statistical epidemiologist1,
  7. Valerie Beral, professor of epidemiology1
  8. on behalf of the Million Women Study collaborators
  1. 1Cancer Epidemiology Unit, University of Oxford, Richard Doll Building, Oxford OX3 7LF
  2. 2Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA
  3. 3Inserm Unit 780, Cardiovascular Epidemiology Section, Villejuif Cedex, France
  4. 4The George Institute for International Health, Sydney NSW, Australia
  1. Correspondence to: V Beral pa.valerie.beral{at}
  • Accepted 14 September 2009


Objective To examine the duration and magnitude of increased risk of venous thromboembolism after different types of surgery.

Design Prospective cohort study (Million Women Study).

Setting Questionnaire data from the Million Women Study linked with hospital admission and death records.

Participants 947 454 middle aged women in the United Kingdom recruited in 1996-2001 and followed by record linkage to routinely collected NHS data on hospital admissions and deaths. During follow-up 239 614 admissions were for surgery; 5419 women were admitted, and a further 270 died, from venous thromboembolism.

Main outcome measures Adjusted relative risks and standardised incidence rates for hospital admission or death from venous thromboembolism (pulmonary embolism or deep vein thrombosis), by time since and type of surgery.

Results Compared with not having surgery, women were 70 times more likely to be admitted with venous thromboembolism in the first six weeks after an inpatient operation (relative risk 69.1, 95% confidence interval 63.1 to 75.6) and 10 times more likely after a day case operation (9.6, 8.0 to 11.5). The risks were lower but still substantially increased 7-12 weeks after surgery (19.6, 16.6 to 23.1 and 5.5, 4.3 to 7.0, respectively). This pattern of risk was similar for pulmonary embolism (n=2487) and deep venous thrombosis (n=3529). The postoperative risks of venous thromboembolism varied considerably by surgery type, with highest relative risks after inpatient surgery for hip or knee replacement and for cancer—1-6 weeks after surgery the relative risks were, respectively, 220.6 (187.8 to 259.2) and 91.6 (73.9 to 113.4).

Conclusion The risk of deep vein thrombosis and pulmonary embolism after surgery is substantially increased in the first 12 postoperative weeks, and varies considerably by type of surgery. An estimated 1 in 140 middle aged women undergoing inpatient surgery in the UK will be admitted with venous thromboembolism during the 12 weeks after surgery (1 in 45 after hip or knee replacement and 1 in 85 after surgery for cancer), compared with 1 in 815 after day case surgery and only 1 in 6200 women during a 12 week period without surgery.


  • We thank the women who participated in the Million Women Study; the study steering committee as well as ISD Scotland, the Information Centre for Health and Social Care, and Northgate Solutions for the linkage of hospital records; and Adrian Goodill for his assistance in the preparation of the figures. A Cancer Research UK studentship supported SS for the duration of her DPhil studies, which included some of the work in this paper. Million Women Study steering committee: Joan Austoker, Emily Banks, Valerie Beral, Judith Church, Ruth English, Jane Green, Julietta Patnick, Richard Peto, Gillian Reeves, Martin Vessey, and Matthew Wallis. Million Women Study coordinating centre staff: Simon Abbott, Miranda Armstrong, Krys Baker, Angela Balkwill, Vicky Benson, Valerie Beral, Judith Black, Anna Brown, Diana Bull, Benjamin Cairns, James Chivenga, Barbara Crossley, Dave Ewart, Sarah Ewart, Lee Fletcher, Laura Gerrard, Adrian Goodill, Isobel Green, Jane Green, Elizabeth Hilton, Joy Hooley, Sau Wan Kan, Carol Keene, Oksana Kirichek, Nicky Langston, Bette Liu, Maria-Jose Luque, Maria MacGregor, Lynn Pank, Kirstin Pirie, Gillian Reeves, Emma Sherman, Evie Sherry-Starmer, Moya Simmonds, Elizabeth Spencer, Helena Strange, Siân Sweetland, Alison Timadjer, Sarah Tipper, Ruth Travis, Xiaosi Wang, Joanna Watson, Stephen Williams, Lucy Wright, Tienyu Yang, and Heather Young. Collaborating UK NHS Breast Screening Centres: Avon, Aylesbury, Barnsley, Basingstoke, Bedfordshire and Hertfordshire, Cambridge and Huntingdon, Chelmsford and Colchester, Chester, Cornwall, Crewe, Cumbria, Doncaster, Dorset, East Berkshire, East Cheshire, East Devon, East of Scotland, East Suffolk, East Sussex, Gateshead, Gloucestershire, Great Yarmouth, Hereford and Worcester, Kent, Kings Lynn, Leicestershire, Liverpool, Manchester, Milton Keynes, Newcastle, North Birmingham, North East Scotland, North Lancashire, North Middlesex, North Nottingham, North of Scotland, North Tees, North Yorkshire, Nottingham, Oxford, Portsmouth, Rotherham, Sheffield, Shropshire, Somerset, South Birmingham, South East Scotland, South East Staffordshire, South Derbyshire, South Essex, South Lancashire, South West Scotland, Surrey, Warrington Halton St Helens and Knowsley, Warwickshire Solihull and Coventry, West Berkshire, West Devon, West London, West Suffolk, West Sussex, Wiltshire, Winchester, Wirral, and Wycombe.

  • Contributors: All authors contributed to the design and conduct of the study and read and approved the final manuscript. VB and SS are the guarantors.

  • Funding: This study was funded by Cancer Research UK (grant No C570/A5028) and the Medical Research Council (grant No G0700474). Marianne Canonico was additionally supported by Leem Recherche. The funders did not participate in the study design and conduct, in the collection, management, analysis and interpretation of the data, nor was there any funder input into the preparation, review or approval of this manuscript.

  • Competing interests: None declared.

  • Ethical approval: This study was approved by the Oxford and Anglia multicentre research and ethics committee.

  • Data sharing: All information provided is stored in accordance with the Data Protection Act (Office of Data Protection Registrar registration No K3039784). Only the study team has access to computerised data, via passwords (see the Million Women Study protocol at

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