Venous thromboembolism in pregnancy: diagnosis, management and prevention

A pregnant woman has a two- to five-fold higher risk of venous thromboembolism (VTE) than a non-pregnant woman of the same age and, in developed countries, she is more likely to die from fatal pulmonary embolism (PE) than from obstetric haemorrhage. The increased VTE risk is mediated through normal physiological changes of pregnancy including alterations in haemostasis that favour coagulation, reduced fibrinolysis and pooling and stasis of blood in the lower limbs. Thrombophilia, smoking, obesity, immobility and postpartum factors such as infection, bleeding and emergency surgery (including emergency caesarian section) also increase the risk of pregnancy-related VTE. The diagnosis of VTE can be safely established with acceptable radiation exposure to the fetus using readily available imaging modalities such as ultrasound, ventilation perfusion lung scanning and computed tomographic pulmonary angiography. However, the optimal diagnostic strategies still remain to be determined. If there is no contraindication to anticoagulation, commencing treatment prior to objective confirmation should be strongly considered. For the mother and fetus, effective and safe treatment is readily available with low-molecular-weight heparin (LMWH), but optimal dosing of these agents in pregnancy remains controversial. Emerging data support antepartum LMWH prophylaxis for women with previous VTE if the event was unprovoked or in the presence of thrombophilia. On the other hand, women with prior provoked VTE and no thrombophilia or women with asymptomatic thrombophilia (but a family history of VTE) can safely be managed with antepartum surveillance. Postpartum prophylaxis is recommended for women with prior VTE or thrombophilia (and a family history of VTE).