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VTE in Obstetrics and Gynaecology

Pregnancy is associated with approximately a 3- to 10-fold higher risk of VTE (OR of 11.4 for VTE events).1 Indeed, fatal thromboembolism continues to be a leading cause of maternal death.2 Unfortunately, the signs and symptoms of VTE during pregnancy are often ignored or inadequately diagnosed, and risk factors are not widely appreciated. As a result, around 50% of cases of VTE that do occur in pregnancy and the post-partum period could have been foreseen and prevented.

There is a known correlation between rates of DVT and gestational age, with DVT risk particularly high in the first 20 weeks, peaking at 29% during weeks 1–5.3 However, fewer than 10% of pregnant women with suspected DVT have their diagnosis confirmed.

Characteristically, DVT in pregnancy is more often left-sided, and usually affects the iliofemoral rather than the popliteofemoral veins. Symptomatic DVT in pregnancy is often associated with lower abdominal pain, mild pyrexia, and leucocytosis.

There are a number of recognized factors that increase risk of VTE in pregnancy.4 These include age over 35 years, Caesarean section, weight > 80 kg, previous thrombosis or family history of VTE, thrombophilia, pre-eclampsia, and artificial reproductive technology.4–7
 
While antithrombotic therapy is often used in pregnancy for VTE prevention, the prevention of systemic embolism in patients with heart-valve prostheses, and the prevention of foetal loss in patients with antiphospholipid syndrome, there are concerns about drug complications for both mother and foetus. Some oral anticoagulants have teratogenic and embryotoxic effects.

A recent systematic review of clinical studies assessing the efficacy and safety of LMWHs for the prevention and treatment of VTE in pregnancy confirms that prophylaxis is effective8 and supports the findings of earlier reviews, which reported a better safety profile and good efficacy for LMWH as compared with UFH for VTE prevention.9,10 In addition, monitoring of pregnant patients receiving thromboprophylaxis is often advised by physicians.

While awareness of the VTE risks associated with Caesarean section has improved in recent decades, gestational VTE is still under-appreciated, and guidelines regarding antenatal prophylaxis and the diagnosis and treatment of VTE in pregnancy have not been translated into everyday practice. Concerns persist that antithrombotic therapy will increase bleeding risk at delivery, and there is uncertainty over the duration of prophylaxis appropriate in pregnancy.

Clinical practice guidelines have been developed for pregnancy and obstetrics and these strongly favour use of LMWH as a preferred anticoagulant agent.11,12

References

  1. Samama MM. An epidemiologic study of risk factors for deep vein thrombosis in medical outpatients: the Sirius study. Arch Intern Med. 2000;160:3415-20.
  2. http://www.cemach.org.uk/
  3. Gherman RB, et al. Incidence, clinical characteristics, and timing of objectively diagnosed venous thromboembolism during pregnancy. Obstet Gynecol. 1999;94:730-4.
  4. McColl MD, Ramsay JE, et al. Risk factors for pregnancy associated venous thromboembolism. Thromb Haemost. 1997;78:1183-8.
  5. Nelson SM, Greer IA. Artificial reproductive technology and the risk of venous thromboembolic disease. J Thromb Haemost. 2006;4:1661-3.
  6. Nelson SM, Greer IA. Thrombophilia and the risk for venous thromboembolism during pregnancy, delivery, and puerperium. Obstet Gynecol Clin North Am. 2006;33:413-27.
  7. Macklon NS, Greer IA. Venous thromboembolic disease in obstetrics and gynaecology: the Scottish experience. Scott Med J. 1996;41:83-6.
  8. Greer IA, Nelson-Piercy C. Low-molecular-weight heparins for thromboprophylaxis and treatment of venous thromboembolism in pregnancy: a systematic review of safety and efficacy. Blood. 2005;106:401-7.
  9. Sanson BJ, Lensing AW, et al. Safety of low-molecular-weight heparin in pregnancy: a systematic review. Thromb Haemost. 1999;81:668-72.
  10. Ensom MH, Stephenson MD. Low-molecular-weight heparins in pregnancy. Pharmacotherapy. 1999;19:1013-25.
  11. Samama CM, Albaladejo P, et al. Venous thromboembolism prevention in surgery and obstetrics: clinical practice guidelines. Eur J Anaesthesiol. 2006;23:95-116.
  12. Bates SM, Greer IA, et al. Use of antithrombotic agents during pregnancy: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest. 2004;126(3 Suppl):627-44S.
 
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