Amniotic fluid embolism (AFE) is a rare but devastating complication of pregnancy characterized by sudden cardiorespiratory collapse and disseminated intravascular coagulation (DIC). Reported incidence varies widely from 1.9 per 100,000 to 6.1 per 100,000 pregnancies based on case reports and autopsy data.¹ Mortality rates range from 24% to 80% in developed countries.² This condition presents suddenly with symptoms ranging from mild organ dysfunction to complete cardiovascular collapse, DIC, and death. Because of its rarity and limited evidence-based research, there are no universally accepted diagnostic criteria. The classic presentation is sudden onset of hypoxia, hypotension, and coagulopathy or bleeding around the time of birth.

First reported in 1926, the clinical sequelae of AFE were originally thought to be obstructive much like a pulmonary embolism. The understanding of the pathophysiology has evolved with the recognition and study of subsequent cases. Currently, the pathogenesis of AFE is thought to be due to an immune-mediated response. The National Amniotic Fluid Embolus Registry was established with the aim of collecting data on all diagnosed cases of AFE in order to contribute to the medical communities’ understanding of this rare disease. Because of the uncommon nature of this disease entity, physicians and institutions have limited experience diagnosing and managing patients with AFE. Although it is not completely understood, knowing the proposed pathophysiology may help providers guide the care of these critically ill patients.

National registry data show that the majority of cases of AFE (approximately 70% of cases) occur during labor. Approximately 19% of cases occur during a cesarean section delivery and 11% occur after vaginal delivery. Rare cases have been reported during the first and second trimesters of pregnancy, at the time of an abortion or miscarriage, as well as during diagnostic procedures such as amniocentesis. Placenta previa, placenta accreta, and abruption all increase the risk for AFE.⁴ AFE may occur up to 48 hours after delivery and should be considered in all postpartum patients who show signs of hemodynamic instability. Other reported risk factors for AFE include multiparity, uterine rupture, eclampsia, advanced maternal age, and polyhydramnios.

AFE most often occurs during labor and delivery; however, it can occur any time there is risk of breach of the maternal-fetal barrier. Uterine trauma or maneuvers to manipulate fetal position within the uterus, such as external cephalic version, risk this disruption.¹ The classic presentation of hypoxia, hypotension, bleeding, and seizure is not always present. Patients with AFE can present with many nonspecific symptoms including hypotension, hypoxia, dyspnea, cough, abdominal pain, chest pain, seizures, and hemorrhage. Patients may initially present with altered mental status or the sensation of impending doom. In the emergency setting, cardiopulmonary arrest may be the patient’s presenting symptom.