Risk of a thrombotic event after the 6-week postpartum period.

BACKGROUND The postpartum state is associated with a substantially increased risk of thrombosis. It is uncertain to what extent this heightened risk persists beyond the conventionally defined 6-week postpartum period. METHODS Using claims data on all discharges from nonfederal emergency departments and acute care hospitals in California, we identified women who were hospitalized for labor and delivery between January 1, 2005, and June 30, 2010. We used validated diagnosis codes to identify a composite primary outcome of ischemic stroke, acute myocardial infarction, or venous thromboembolism. We then used conditional logistic regression to assess each patient's likelihood of a first thrombotic event during sequential 6-week periods after delivery, as compared with the corresponding 6-week period 1 year later. RESULTS Among the 1,687,930 women with a first recorded delivery, 1015 had a thrombotic event (248 cases of stroke, 47 cases of myocardial infarction, and 720 cases of venous thromboembolism) in the period of 1 year plus up to 24 weeks after delivery. The risk of primary thrombotic events was markedly higher within 6 weeks after delivery than in the same period 1 year later, with 411 events versus 38 events, for an absolute risk difference of 22.1 events (95% confidence interval [CI], 19.6 to 24.6) per 100,000 deliveries and an odds ratio of 10.8 (95% CI, 7.8 to 15.1). There was also a modest but significant increase in risk during the period of 7 to 12 weeks after delivery as compared with the same period 1 year later, with 95 versus 44 events, for an absolute risk difference of 3.0 events (95% CI, 1.6 to 4.5) per 100,000 deliveries and an odds ratio of 2.2 (95% CI, 1.5 to 3.1). Risks of thrombotic events were not significantly increased beyond the first 12 weeks after delivery. CONCLUSIONS Among patients in our study, an elevated risk of thrombosis persisted until at least 12 weeks after delivery. However, the absolute increase in risk beyond 6 weeks after delivery was low. (Funded by the National Institute of Neurological Disorders and Stroke.).

[1]  M. Wintermark,et al.  Guidelines for the Early Management of Patients With Acute Ischemic Stroke: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association , 2013, Stroke.

[2]  Samy Suissa,et al.  The case-crossover study design in pharmacoepidemiology , 2009, Statistical methods in medical research.

[3]  J. West,et al.  Risk of first venous thromboembolism in and around pregnancy: a population‐based cohort study , 2012, British journal of haematology.

[4]  E. Myers,et al.  Incidence and Risk Factors for Stroke in Pregnancy and the Puerperium , 2005 .

[5]  D. Veenstra,et al.  Evidence-Based Clinical Practice Guidelines ed: American College of Chest Physicians Therapy and Prevention of Thrombosis, 9th Therapy, and Pregnancy : Antithrombotic VTE, Thrombophilia, Antithrombotic , 2012 .

[6]  E. Myers,et al.  Acute Myocardial Infarction in Pregnancy: A United States Population-Based Study , 2006, Circulation.

[7]  Louette R. Johnson Lutjens.  Research , 2006 .

[8]  S. Middeldorp.  Thrombosis in women: what are the knowledge gaps in 2013? , 2013, Journal of thrombosis and haemostasis : JTH.

[9]  Gordon H Guyatt,et al.  Executive Summary Antithrombotic Therapy and Prevention of Thrombosis , 9 th ed : American College of Chest Physicians Evidence-Based Clinical Practice Guidelines , 2012 .

[10]  Paolo Prandoni,et al.  Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. , 2012, Chest.

[11]  W. Longstreth,et al.  Validating Administrative Data in Stroke Research , 2002, Stroke.

[12]  Karen L. Furie,et al.  Response to Letter by Naylor Regarding Article, “Guidelines for the Prevention of Stroke in Patients With Stroke or Transient Ischemic Attack: A Guideline for Healthcare Professionals From the American Heart Association/American Stroke Association” , 2011 .

[13]  E. Myers,et al.  Venous thromboembolism during pregnancy and the postpartum period: incidence, risk factors, and mortality. , 2006, American journal of obstetrics and gynecology.

[14]  Sebastian Schneeweiss,et al.  Accuracy of Medicare claims-based diagnosis of acute myocardial infarction: estimating positive predictive value on the basis of review of hospital records. , 2004, American heart journal.

[15]  S. Bewley,et al.  Incidence, Risk Factors, Management, and Outcomes of Stroke in Pregnancy , 2012, Obstetrics and gynecology.

[16]  M. Blombäck,et al.  Changes in blood coagulation and fibrinolysis in the normal puerperium. , 1985, Gynecologic and obstetric investigation.

[17]  F. Pipkin,et al.  A longitudinal study of platelet behaviour and thromboxane production in whole blood in normal pregnancy and the puerperium , 1990, British journal of obstetrics and gynaecology.

[18]  O. Hovatta,et al.  Incidence of pulmonary and venous thromboembolism in pregnancies after in vitro fertilisation: cross sectional study , 2013, BMJ.

[19]  C. Steiner,et al.  Comorbidity measures for use with administrative data. , 1998, Medical care.

[20]  M Maclure,et al.  Should we use a case-crossover design? , 2000, Annual review of public health.

[21]  M. Elkind,et al.  Dural sinus thrombosis presenting three months postpartum. , 2003, Annals of emergency medicine.

[22]  G. Guyatt,et al.  Physicians Evidence-Based Clinical Practice Development : American College of Chest Thrombolytic Therapy Guideline Methodology for Antithrombotic and , 2008 .

[23]  E. Vicaut,et al.  Extended-Duration Venous Thromboembolism Prophylaxis in Acutely Ill Medical Patients With Recently Reduced Mobility , 2010, Annals of Internal Medicine.

[24]  L. Tengborn,et al.  APC Resistance and other Haemostatic Variables during Pregnancy and Puerperium , 1999, Thrombosis and Haemostasis.

[25]  Carl J Pepine,et al.  ACC/AHA guideline update for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction--2002: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients , 2002, Circulation.

[26]  J. Douketis,et al.  Extended-duration prophylaxis against venous thromboembolism after total hip or knee replacement: a meta-analysis of the randomised trials , 2001, The Lancet.

[27]  D. Veenstra,et al.  VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. , 2012, Chest.

[28]  R. Macko,et al.  Pregnancy and the risk of stroke , 1996, New England Journal of Medicine.

[29]  Nancy M Albert,et al.  2012 ACCF/AHA focused update incorporated into the ACCF/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. , 2013, Journal of the American College of Cardiology.

[30]  P. Lichtenstein,et al.  Increased Risks of Circulatory Diseases in Late Pregnancy and Puerperium , 2001, Epidemiology.

[31]  K. Bailey,et al.  Trends in the Incidence of Venous Thromboembolism during Pregnancy or Postpartum: A 30-Year Population-Based Study , 2005, Annals of Internal Medicine.

[32]  F. Rosendaal,et al.  Pregnancy, the postpartum period and prothrombotic defects: risk of venous thrombosis in the MEGA study , 2008, Journal of thrombosis and haemostasis : JTH.

[33]  S Suissa,et al.  The Case‐Time‐Control Design: Further Assumptions and Conditions , 1998, Epidemiology.

[34]  C. Bushnell,et al.  Migraines during pregnancy linked to stroke and vascular diseases: US population based case-control study , 2009, BMJ : British Medical Journal.

[35]  P. Romano,et al.  Predictors of rehospitalization for symptomatic venous thromboembolism after total hip arthroplasty. , 2000, The New England journal of medicine.

[36]  D. Singer,et al.  A new risk scheme to predict warfarin-associated hemorrhage: The ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation) Study. , 2011, Journal of the American College of Cardiology.