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Common risk factors for venous thromboembolism (VTE) are older age, obesity, previous thrombosis, immobilization, surgery, and pregnancy. Pregnant patients occasionally have more than one VTE risk factor, such as obesity and cesarean (C)-section surgery.
Is the risk high enough in pregnant patients to justify giving anticoagulant prophylaxis pre- or postpartum? To address this question, UK investigators reviewed 376,000 pregnancies in 280,000 women from the medical records of 1500 general practitioners.
The overall incidence of antepartum and postpartum VTE was 84 and 338 per 100,000 person-years, respectively. Among antepartum women, adjusted incidence rate ratios (IRRs) were significantly higher in those with diabetes (3.54), inflammatory bowel disease (3.50), varicose veins (2.21), and urinary tract infection (1.80) than in those without these conditions. Among postpartum women, IRRs increased with increasing age and body-mass index (BMI) and were significantly higher in those having cardiac disease (5.30), inflammatory bowel disease (4.07), varicose veins (3.90), obstetrical hemorrhage (2.53), preterm birth (2.28), 3 or more previous deliveries (1.92), and C-section (1.88). The highest risks for VTE were associated with postpartum BMI ≥40 kg/m2 and antepartum diabetes (221 and 180 per 100,000 pregnancies, respectively). Other postpartum risk factors were a BMI 30 to 40 kg/m2 (143), varicose veins (188), and stillbirth accompanied by other risk factors (523).
Sultan AA et al. Risk factors for first venous thromboembolism around pregnancy: A population based cohort study from the United Kingdom. Blood 2013 May 9; 121:3953. (http://dx.doi.org/10.1182/blood-2012-11-469551)
Gris J-CR. Risk factors for first venous thromboembolism around pregnancy: Some practical considerations. Blood 2013 Apr 25; [e-pub ahead of print]. (http://viajwat.ch/11uWQlX)
Comment
This large population-based cohort study shows that the impact of VTE risk factors is greater postpartum than antepartum. The study results suggest that thromboprophylaxis should be considered for postpartum women with a BMI ≥30 kg/m2, varicose veins, or a stillbirth, as well as with one or more other risk factors, such as obstetrical hemorrhage, preterm birth, C-section, and other comorbidities. However, an accompanying letter notes that more than 2000 women with a stillbirth—and even larger numbers of those with obesity, preterm birth, C-section, and obstetric hemorrhage—would need to be treated postpartum to prevent one VTE. Given the current state of knowledge, it is probably best to avoid blanket recommendations for all pregnancies and, instead, implement thromboprophylaxis on a case-by-case basis.