19: Embolic Disorders of Pregnancy and Amniotic Fluid Embolism

THROMBOEMBOLIC DISORDERS

Epidemiology

Pregnancy imparts a four fold to five fold increased risk of thromboembolism when compared to the nonpregnant state.¹ This risk rises to a 20-fold increase during the postpartum period and does not return to nonpregnant levels until approximately 6 weeks’ postpartum.^1,2 The majority of thromboembolic events in pregnancy are venous in origin. The incidence of venous thromboembolism (VTE) in pregnant women is estimated to be 5 to 12 events per 10,000 pregnancies, evenly distributed between the time period from conception to delivery.¹ The mortality from pregnancy related VTE is 1.1 deaths per 100,000, an estimate of about 10% of all maternal deaths.³

Types of Venous Thromboembolism

Venous thromboembolism in pregnancy is commonly manifested as pulmonary embolism or as deep venous thrombosis (DVT). DVT accounts for 80% of thromboembolic cases, while pulmonary embolism is responsible for the remaining 20%.⁴

Pulmonary Embolism

Pulmonary embolism (PE) is the leading cause of direct maternal deaths in developed countries, and it accounts for 20% of pregnancy-related deaths.³ The incidence of PE is 0.01% to 0.05% of all pregnancies, and the risk is greater in the postpartum period, with 43% to 60% of pregnancy-related episodes occurring 4 to 6 weeks postpartum. PE after cesarean delivery is higher than after vaginal delivery by a factor of 2.5 to 20, and the incidence of fatal PE is higher by a factor of 10.²

Deep Venous Thrombosis

The incidence of DVT is 0.02% to 0.36% of all pregnancies. A meta-analysis showed that two-thirds of cases of DVT occur antepartum and are equally distributed across trimesters.⁵ Pregnancy-associated DVT is left sided in more than 85% of cases. The mechanism for this predilection for the left leg is probably related to compression of the left iliac vein by the right iliac artery and the gravid uterus (Figure 19-1).¹

Pelvic Vein Thrombosis

Isolated pelvic vein thrombosis (PVT) is more common in pregnancy. According to a multicenter prospective registry, 11% (6 of 53) of pregnant or postpartum women with DVT had isolated PVT compared with 1% (17 of 5451) of nonpregnant patients.¹ Ovarian vein thrombosis, a form of septic PVT, may complicate less than 0.05% of vaginal deliveries and up to 1% to 2% of cesarean deliveries. In 90% of cases, PVT occurs within 10 days’ postpartum but can occur up to 10 weeks’ postpartum. Symptoms include fever unresponsive to antibiotics (80%), ...