Epidemiology – Venous thromboembolism (VTE) occurs in pregnant women at 7-10 times the incidence in age-matched controls. Pregnant women who get VTE have deep venous thrombosis (DVT) approximately 3 times as often as pulmonary embolism (PE). The increased risk is similar during all three trimesters, starts to diminish after delivery, and returns to baseline by six weeks post-partum. The left leg is affected in 85% of pregnancy-associated DVT, possibly from compression of the left iliac vein. Isolated pelvic DVT is also more common in pregnancy. In the developed world, pregnancy-associated VTE is the leading cause of maternal mortality.

Source: Diagnosing PE in Pregnant Women — Brown Emergency Medicine