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Amniotic fluid embolism (AFE) represents a rare but catastrophic obstetric emergency characterized by abrupt cardiorespiratory collapse and disseminated intravascular coagulation. Often termed the anaphylactoid syndrome of pregnancy, this condition reflects a profound inflammatory and immune-mediated response rather than a true mechanical embolism. In the United States, AFE remains the second leading cause of peripartum maternal death and the primary cause of peripartum cardiac arrest, affecting 2.2 to 7.7 per 100,000 deliveries and contributing to 7.5% of maternal deaths. This course outlines the typical presentation of AFE, which includes sudden hypoxia, hypotension, altered mental status, seizures, and severe coagulopathy, frequently progressing within minutes as its complications, including long-term cardiac, neurologic, renal, and pulmonary sequelae. This activity reviews the diagnostic criteria, including consensus guidance from the Society for Maternal-Fetal Medicine, exclusionary diagnoses, and evidence-based resuscitation of AFE. Participants will gain an understanding of coordinated cardiopulmonary resuscitation, hemodynamic optimization, massive transfusion strategies, and timely resuscitative hysterotomy. This activity for healthcare professionals is designed to enhance the learner's competence in identifying AFE, understanding its distinct pathophysiology, recognizing initial clinical indicators, performing the recommended evaluation, coordinating simulation-based preparedness, and implementing an appropriate interprofessional approach when managing this condition to improve maternal and neonatal outcomes. Objectives: Identify the early warning signs associated with amniotic fluid embolism. Differentiate amniotic fluid embolism from other causes of peripartum cardiopulmonary collapse. Implement evidence-based cardiopulmonary resuscitation strategies specific to pregnancy, including preparation for resuscitative hysterotomy. Collaborate in improving care coordination among an interprofessional team to improve outcomes for a patient affected by an amniotic fluid embolism. Access free multiple choice questions on this topic.

Amniotic fluid embolism (AFE) constitutes a catastrophic obstetric emergency characterized by sudden cardiorespiratory collapse and disseminated intravascular coagulation (DIC). Frequently described as the anaphylactoid syndrome of pregnancy, AFE differs from a true mechanical embolism and does not result solely from the presence of amniotic fluid.[1][2] Global occurrence ranges from 1 in 8,000 to 1 in 80,000 deliveries, although precise incidence remains uncertain due to diagnostic challenges and reporting inaccuracies.[2] Within the United States, AFE represents the second leading cause of peripartum maternal death and the primary cause of peripartum cardiac arrest. Clinical presentation develops abruptly, most often with sudden cardiovascular and respiratory collapse, altered mental status, and rapid progression to severe coagulopathy.[1] Survivors frequently experience significant cardiac, renal, neurologic, and pulmonary dysfunction. In the United States, AFE occurs in 2.2 to 7.7 per 100,000 deliveries and accounts for 7.5% of maternal deaths. Mortality in developing countries ranges from 1.8 to 5.9 per 100,000 deliveries, compared with 0.5 to 1.7 per 100,000 deliveries in developed countries.[1] The first description of AFE appeared in 1941 when Steiner and Luschbaugh identified fetal cells within the maternal pulmonary circulation of women who died during labor.[1][3] Data from the National Amniotic Fluid Embolism Registry demonstrate pathophysiologic features resembling anaphylaxis rather than classic embolic obstruction. Fetal tissue or amniotic fluid components do not consistently appear in affected patients.[1] Historically, diagnosis relied on postmortem identification of fetal squamous cells in maternal blood from the pulmonary artery.[4] Because fetal squamous cells also circulate in laboring women without AFE, clinicians now establish the diagnosis through exclusion, guided by characteristic clinical presentation after eliminating alternative causes of hemodynamic instability.[5]

AFE demonstrates an unpredictable course and an elusive origin. Multiple factors contribute to its development, including maternal age older than 35 to 40 years, grand multiparity, male fetuses, early gestational age, cervical ripening, polyhydramnios, multiple gestation, gestational diabetes, operative delivery, manual placental extraction, regional variation in the western United States, Asian and Black races, asthma, illicit substance use, and trauma.[6] Induction of labor and comorbidities such as cerebrovascular disorders and cardiac disease further increase risk. Strong associations also involve placenta previa, eclampsia, uterine rupture, fetal growth restriction, fetal death, placental abruption, maternal renal disease, peripartum cardiomyopathy, and postpartum hemorrhage.[6] Evidence regarding certain risk factors remains conflicting.[7] Earlier studies linked cesarean delivery, particularly with a classical uterine incision, to increased risk; subsequent analyses found no association with cesarean delivery of any type. Amniotomy once appeared to elevate risk, but now shows no clear relationship. A population-based case-cohort study evaluating 149 AFE cases, including 80 fatalities, reported that spontaneous vaginal delivery carried 12 times the risk compared with cesarean delivery, while instrumental vaginal delivery carried nearly 3 times the risk. Investigators concluded that cesarean section functions as a protective factor for fatal AFE.[3] Amnioinfusion correlates with a 3-fold increase in risk, possibly related to uterine distension.[6] Prior allergies occurred in 66% of affected patients, exceeding baseline atopy rates and supporting the term anaphylactoid syndrome of pregnancy. In vitro fertilization accounted for 8% of AFE cases, surpassing the baseline IVF rate.[6] Placenta accreta spectrum disorder shows the strongest association, conferring a 10-fold increased risk, with higher incidence paralleling greater severity.[6][8] Entry of amniotic fluid and fetal components into maternal circulation provokes intense pulmonary vasoconstriction and bronchoconstriction. These responses arise primarily from inflammatory cytokine release triggered by exposure to foreign material rather than simple mechanical obstruction.[8] The resultant mediator activity activates the coagulation and fibrinolytic pathways, culminating in DIC.[6]

The estimated incidence of AFE ranges from 1.9 to 6.1 per 100,000 births, though the exact prevalence remains uncertain due to inaccurate diagnosis and underreporting of nonfatal cases.[9][10] Notably, AFE emerged as the primary cause of death during parturition in Germany in 2011 and accounts for 24.3% of maternal deaths in Japan.[10] In Australia, AFE is recognized as the leading direct cause of maternal mortality, affecting between 1 in 8000 and 1 in 80,000 deliveries. The estimated incidence in the United Kingdom is 2 per 100,000 births, while in the United States, AFE occurs at approximately 7.7 per 100,000 births.[10] Race seems to be related to the risk of AFE, with roughly 15% being Hispanic, 7% Asian or Pacific Islander, 44% being Caucasian, 21% being black, and 10% being other races.[11] A significant majority of AFE cases, around 70%, manifest during labor, with approximately 19% occurring during cesarean sections and 11% following vaginal deliveries. Notably, AFE can occur up to 48 hours after delivery.[10] Rare instances of AFE have been reported after pregnancy termination, amniocentesis, injection of hypertonic saline into the uterus for abortion induction, and in the first or second trimester of pregnancy.[5]

AFE involves disruption of the placental-amniotic interface, permitting amniotic fluid and fetal elements, including hair, meconium, skin cells, and gut mucin, to enter the maternal circulation. Detection of squamous cells within the pulmonary vasculature no longer serves as the sole diagnostic criterion, as clinical presentation is central to diagnosis.[12][13][7] Entry of amniotic and fetal material introduces tissue factors with potent procoagulant properties.[12] Activation of histamine, endothelin, and leukotrienes produces physiologic changes culminating in cardiovascular collapse.[14] Potential routes of entry include the placental attachment site, cervical veins, and uterine surgical incisions. Once these substances reach the pulmonary arterial circulation, a pathologic maternal anaphylactoid immune response ensues, accompanied by the release of inflammatory mediators.[12] The initial phase features intense, transient pulmonary vasoconstriction, sometimes accompanied by bronchoconstriction. Acute pulmonary arterial obstruction follows, along with dilation of the right ventricle and right atrium and significant tricuspid regurgitation. Hypoxia and right heart failure subsequently develop. A less common presentation manifests primarily with hemorrhage and DIC without maternal hemodynamic instability.[4][12] Progressive right ventricular enlargement leads to marked depression of left ventricular function, driven by myocardial ischemia related to hypoxia or coronary artery spasm. Septal bowing into the left ventricle produces obstruction and systolic dysfunction, increasing pulmonary artery pressure and reducing cardiac output.[7] Reported dysrhythmias include ventricular fibrillation, asystole, and pulseless electrical activity. Survivors may sustain hypoxic brain injury or multisystem organ failure.[15]

Progressive right ventricular enlargement leads to marked depression of left ventricular function, driven by myocardial ischemia related to hypoxia or coronary artery spasm. Septal bowing into the left ventricle produces obstruction and systolic dysfunction, increasing pulmonary artery pressure and reducing cardiac output.[7] Reported dysrhythmias include ventricular fibrillation, asystole, and pulseless electrical activity. Survivors may sustain hypoxic brain injury or multisystem organ failure.[15] Hypoxemia and hypotension precipitate sudden cardiovascular collapse. Amniotic fluid and fetal components stimulate the release of inflammatory mediators, including platelet-activating factor, tissue necrosis factor-alpha (TNF-alpha), interleukin 6, interleukin 1, phospholipase A2, endothelin, plasminogen activators, thromboplastins, and complement factors.[15] This cascade activates coagulation and fibrinolytic pathways, producing a fibrinolytic form of DIC. Amniotic fluid activates platelet factor III, promoting platelet aggregation and activation of clotting factor Xa. Infiltration of the uterus by amniotic and fetal elements may provoke severe uterine atony, worsening hemorrhage. Pathologic activation of coagulation and fibrinolysis results in severe coagulopathy in approximately 80% of patients.[15] Coagulation factor depletion may occur immediately during cardiopulmonary collapse or emerge later. Hemorrhage often proves severe, persistent, and fatal. Autopsy findings in fatal cases include pulmonary edema, amniotic component emboli within the lungs, and alveolar hemorrhage. Additional observations may include myocardial infarction, acute renal failure due to acute tubular necrosis, and cerebral infarctions.

Histopathologic observations emphasize the complex macroscopic and microscopic pathology of AFE and reinforce the need for comprehensive evaluation when diagnosing and studying this life-threatening obstetric emergency. Prevalence of Pulmonary Edema Pulmonary edema appears in 70% of postmortem examinations of individuals who die from AFE, representing a prominent and clinically significant pathological feature. This high prevalence underscores its central role in the disease process and highlights its importance during autopsy evaluation. Microscopic Presence of Amniotic Fluid Substances Amniotic fluid components often appear within the pulmonary vasculature; however, microscopic identification may be difficult due to their small size. Histologic evaluation does not consistently detect these small particles, which may contribute to underrecognition during pathologic assessment.[16] Alveolar Hemorrhage Alveolar hemorrhage commonly accompanies pulmonary edema and represents another frequent histologic finding in affected lungs. Recognition of alveolar hemorrhage further characterizes the spectrum of pulmonary injury associated with AFE.

Clinical History The medical history or current health details of a patient experiencing an AFE may reveal factors, eg, advanced maternal age, multiple pregnancies, placenta-related issues (accreta, abruption, previa), preeclampsia, gestational diabetes, polyhydramnios, amniocentesis, use of amnioinfusion, amniotomy, cervical lacerations, or any surgery on the gravid uterus.[17] In the classic scenario, women in the later stages of labor suddenly develop acute shortness of breath accompanied by hypotension. Preceding other symptoms, there may be signs of agitation, anxiety, altered mental status, or a sense of impending doom. Seizures may ensue, leading to cardiac arrest, followed by massive hemorrhage associated with DIC, ultimately resulting in death—often within an hour of onset. Statistics indicate that 53% of females with AFE present at or just before delivery, while the remainder present, on average, 19 minutes after delivery.[17] Physical Examination AFE commonly manifests with cardiac arrest, but other presentations include respiratory collapse and DIC. Many patients lose consciousness, and some may exhibit seizure-like activity (10% to 50%), likely due to brain anoxia.[17] The physical examination typically reveals a patient in cardiovascular collapse, marked by severe hypoxemia, hypotension, and cyanosis. The classic triad of AFE consists of hypoxia, hypotension, and coagulopathy, with a normal body temperature.[3] Funduscopic examination may detect minute bubbles in retinal arteries. Tachypnea may be present, often accompanied by the characteristic holosystolic high-pitched murmur of tricuspid regurgitation. This murmur is loudest at the lower left sternal border, radiating to the right sternal edge. Hemorrhage can range from massive to minimal, and uterine atony (83%) exacerbates bleeding. Initial bleeding typically occurs from the vagina but may also be observed in surgical incisions. Full-blown DIC is observed in approximately 83% of patients. Premonitory symptoms, such as shortness of breath or agitation, may precede cardiovascular collapse.[17]

The diagnosis of AFE relies on exclusionary criteria following a clinical scenario consistent with its characteristics.[18] AFE is fundamentally a clinical diagnosis, as no reliable, definitive test for AFE exists. The characteristic clinical pattern of AFE is marked by abrupt hypotension or cardiopulmonary collapse, evidence of disseminated intravascular coagulation, lack of fever, and occurrence during labor or shortly after delivery.[19] The suspicion of AFE initially arises when sudden dyspnea, dysphoria, hypotension, cardiovascular collapse, and coagulopathy manifest following actions during the peripartum period, eg, or after elective pregnancy terminations, whether induced or surgical.[20] Initial evaluation typically occurs during aggressive cardiopulmonary resuscitation, focusing on the 2 main system failures: hemodynamic and hematologic.[18] Transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) plays a crucial role in diagnosis when available. TEE is preferred if patient stability is achieved. Significant echocardiographic findings in AFE include right ventricle dilatation, hypokinesis, overload, tricuspid regurgitation, and right atrial enlargement.[18] Early cardiac thrombi may be identified in the enlarged right ventricle or right atrium.[7] A characteristic feature associated with AFE is the bowing of the intraventricular septum into the left ventricle, leading to left ventricular obstruction and systolic dysfunction, resembling the shape of the letter "D."[18] Immediate blood collection is essential for an urgent type and crossmatch, complete blood count, comprehensive metabolic panel, and a full coagulation panel, encompassing platelets, prothrombin time, partial thromboplastin time, bleeding time, fibrinogen, d-dimer, and fibrin degradation products.[18] The International Society on Thrombosis and Hemostasis (ISTH) provides a formal scoring system to determine the presence of DIC in pregnancy based on platelet count, international normalized ratio (INR), and fibrinogen level. Scores greater than 3 indicate the presence of DIC in pregnancy.[21][18] Amniotic Fluid Embolism Diagnostic Criteria

Immediate blood collection is essential for an urgent type and crossmatch, complete blood count, comprehensive metabolic panel, and a full coagulation panel, encompassing platelets, prothrombin time, partial thromboplastin time, bleeding time, fibrinogen, d-dimer, and fibrin degradation products.[18] The International Society on Thrombosis and Hemostasis (ISTH) provides a formal scoring system to determine the presence of DIC in pregnancy based on platelet count, international normalized ratio (INR), and fibrinogen level. Scores greater than 3 indicate the presence of DIC in pregnancy.[21][18] Amniotic Fluid Embolism Diagnostic Criteria Establishing precise criteria for diagnosing AFE has been challenging due to the absence of a single definitive test. Various international standards have been introduced to define AFE, with the American Society for Maternal-Fetal Medicine (SMFM) establishing objective criteria following a consensus symposium with the Amniotic Fluid Embolism Foundation in 2016.[21] The criteria stipulate the presence of the following conditions: Sudden cardiopulmonary collapse or hypotension (systolic blood pressure <90 mm Hg) with hypoxia (SpO2 <90%). Severe hemorrhage or DIC according to the ISTH definition. Symptomatology occurs either during labor or placental delivery (or up to 30 minutes later). Absence of fever or other explanations for the observed findings [14][22] The SMFM acknowledges that cases may fall outside these parameters, eg, during pregnancy terminations. They clarify that their primary objective is to establish standardized criteria for research reporting. While recognizing that their standards may encompass numerous outlier cases, they hope to minimize such occurrences.[22] The critical clinical findings associated with AFE include coagulopathy, pulmonary hypertension, and neurologic symptoms. Some authors have proposed a modified version of the above definition that would consist of premonitory signs, eg, seizures, agitation, anxiety, feelings of imminent death, confusion, and fainting. Some authors have suggested that the diagnostic criteria proposed by SMFM should be further validated in future large prospective cohort studies.[21]

Due to the rarity of AFE, many obstetric clinicians lack experience in managing such cases. To mitigate panic and confusion and enhance coordination among healthcare practitioners, a checklist has been proposed as a beneficial cognitive aid for the initial and immediate management of a patient with an AFE.[23] The overall treatment approach for a patient with an AFE is supportive, with initial management aligned with the "ABC" principles, prioritizing airway, breathing, and circulation support.[23] Initial Management Prompt and effective cardiopulmonary resuscitation is the cornerstone of managing an acute AFE. Chest compressions should be initiated immediately, providing 100 to 120 compressions per minute with 1 ventilation every 6 seconds. Avoiding excessive ventilation is crucial, as this can lead to a decrease in cardiac output.[23] During chest compressions, defibrillator pads should be applied without interruption, and a nonsynchronized shock should be administered if the cardiac rhythm is shockable. Cardiopulmonary resuscitation should continue for 2 minutes, followed by a pause to check for a pulse and analyze the rhythm. Changing clinicians is recommended to ensure that no one person provides chest compressions for more than 2 minutes.[23] If indicated, a second shock may be administered, and the process should be repeated. For the mother, comprehensive care includes securing the airway, ensuring effective ventilation, managing fluids appropriately, and judiciously using vasopressors. Intra-arterial lines facilitate real-time pressure measurement and frequent arterial blood gas sampling. A central venous pressure line aids in assessing right-sided preload. Recognizing the adverse impact of copious fluid administration on clotting factors and bleeding, the decision to transition to vasopressors should be contemplated earlier, as compared to later, when resuscitating a patient with significant bleeding from other causes.[23]

For the mother, comprehensive care includes securing the airway, ensuring effective ventilation, managing fluids appropriately, and judiciously using vasopressors. Intra-arterial lines facilitate real-time pressure measurement and frequent arterial blood gas sampling. A central venous pressure line aids in assessing right-sided preload. Recognizing the adverse impact of copious fluid administration on clotting factors and bleeding, the decision to transition to vasopressors should be contemplated earlier, as compared to later, when resuscitating a patient with significant bleeding from other causes.[23] In the absence of intravenous (IV) access, establishing an interosseous line in the humeral head is advised for fluid and medication administration. If the cardiac rhythm persists, epinephrine at a dose of 1 mg every 3 to 5 minutes should be administered via the IV or interosseous line.[23] In the presence of cardiac arrest with no return of circulation within approximately 4 minutes, preparations for delivery should be made. This can involve an operative delivery or perimortem cesarean delivery if the fetus is at a gestational age considered viable.[23] The release of vasoconstrictors often increases pulmonary vascular resistance, leading to right ventricular failure. TTE findings can help recognize this failure. Managing right ventricular failure involves adjusting ventilator settings, avoiding fluid overload, and using medications such as norepinephrine to control blood pressure. Preferred inotropic support includes dobutamine or milrinone, and vasodilation with epoprostenol is recommended.[23]

The release of vasoconstrictors often increases pulmonary vascular resistance, leading to right ventricular failure. TTE findings can help recognize this failure. Managing right ventricular failure involves adjusting ventilator settings, avoiding fluid overload, and using medications such as norepinephrine to control blood pressure. Preferred inotropic support includes dobutamine or milrinone, and vasodilation with epoprostenol is recommended.[23] Coagulopathy induced by tissue factor activation, primarily through Factor VII activation, should be addressed with a 1:1:1 ratio of packed red blood cells, platelets, and fresh frozen plasma to maintain fibrinogen levels above 150 mg/dL to 200 mg/dL.[23] Tranexamic acid should be given promptly, as this antifibrinolytic is readily available and safe to use with obstetrical hemorrhage.[24] Treating with large volumes of fluid should be avoided. If prolonged CPR of 10 minutes or longer is needed, or if right ventricular failure is unresponsive to medical management, consideration may be given to extracorporeal membrane oxygenation (ECMO). Anticoagulation treatment may be necessary to reduce activation of coagulation, platelet consumption, and consumption of coagulation factors.[23] Obstetrical Management The prompt evacuation of the fetus, termed "resuscitative hysterotomy," is a pivotal component of AFE treatment, distinct from perimortem cesarean section, with the primary aim of improving maternal hemodynamics. Given its time-sensitive nature, this procedure is likely to be conducted at the site of the AFE, as transport to an operating room within the optimal 1- to 2-minute window may not be feasible.[23] Obstetrical management must prioritize the rapid evacuation of the fetus, usually by cesarean section. The Society for Maternal-Fetal Medicine recommends this for all fetuses over 23 weeks of gestational age. Evacuation of the uterus may not improve the clinical situation with a previable fetus or even with a gestational age of less than 20 weeks. Ongoing resuscitation of the mother in the delivery room, with an anesthesiologist or critical care clinicians overseeing cardiovascular resuscitation, must continue during the infant's extraction. Shifting the gravid uterus to the left is recommended, relieving aortocaval compression.[23]

Obstetrical management must prioritize the rapid evacuation of the fetus, usually by cesarean section. The Society for Maternal-Fetal Medicine recommends this for all fetuses over 23 weeks of gestational age. Evacuation of the uterus may not improve the clinical situation with a previable fetus or even with a gestational age of less than 20 weeks. Ongoing resuscitation of the mother in the delivery room, with an anesthesiologist or critical care clinicians overseeing cardiovascular resuscitation, must continue during the infant's extraction. Shifting the gravid uterus to the left is recommended, relieving aortocaval compression.[23] This interprofessional team, capable of initiating neonatal resuscitation, should include a neonatologist, given that the majority of these infants are born with a low Apgar score. The obstetrician may opt for several procedures to alleviate ongoing uterine hemorrhage, such as uterine artery ligation or embolization. Circumferential B-Lynch, Hayman, or Pereira compression sutures have been used to compress the atonic uterus and staunch bleeding. However, in the setting of massive hemorrhage and an atonic uterus, emergency hysterectomy may be the best course, required in approximately 50% of patients with severe and ongoing coagulopathy.[23] Laboratory Surveillance Standard laboratory turnaround times for monitoring clotting parameters may be too slow for actively bleeding patients. Viscoelastic hemostatic assay (VHA)-guided algorithms have demonstrated reduced transfusion requirements, offering improved outcomes. Whole blood viscoelastic hemostatic assays, eg, thromboelastography and rotational thromboelastometry, performed at the bedside, provide minute-to-minute evaluation of clinically relevant information, aiding in the rapid assessment and treatment of major obstetric hemorrhage, as seen in AFE. These measurements include fibrinogen levels, platelet count and function, and evaluation of the entire extrinsic clotting pathway, guiding appropriate administration of cryoprecipitate, fibrinogen, prothrombin complex concentrates, platelets, FFP, and pRBCs.[23] Management of Pulmonary Hypertension and Right Heart Failure

Standard laboratory turnaround times for monitoring clotting parameters may be too slow for actively bleeding patients. Viscoelastic hemostatic assay (VHA)-guided algorithms have demonstrated reduced transfusion requirements, offering improved outcomes. Whole blood viscoelastic hemostatic assays, eg, thromboelastography and rotational thromboelastometry, performed at the bedside, provide minute-to-minute evaluation of clinically relevant information, aiding in the rapid assessment and treatment of major obstetric hemorrhage, as seen in AFE. These measurements include fibrinogen levels, platelet count and function, and evaluation of the entire extrinsic clotting pathway, guiding appropriate administration of cryoprecipitate, fibrinogen, prothrombin complex concentrates, platelets, FFP, and pRBCs.[23] Management of Pulmonary Hypertension and Right Heart Failure Pulmonary hypertension and right heart failure commonly accompany AFE, making inotropes, pulmonary vasodilators, and afterload-reducing agents paramount to treatment.[23] Vasopressor support should be initiated with norepinephrine if needed. Dobutamine and milrinone, as inotropes, provide pulmonary vasculature dilation and a decrease in right ventricular afterload. Epoprostenol, whether inhaled or intravenously, for pulmonary vasodilation may be used instead of inhaled nitric oxide or sildenafil, with similar outcomes in right ventricular failure.[23] Ideal management involves maintaining a mean arterial pressure (MAP) greater than 65 mm Hg, a cardiac index greater than 2 L per meter squared, an adequate urine output of 40 mL/hr to 50 mL/hr, and a PaO2/FiO2 ratio more than 250. Extracorporeal Membrane Oxygenation Extracorporeal membrane oxygenation (ECMO) life support has proven successful for refractory cardiogenic shock secondary to AFE when severe right ventricular dysfunction does not respond to medical management.[23] ECMO provides respiratory and hemodynamic support through the femoral vasculature until the right ventricle's function improves. Any patient persisting in cardiopulmonary collapse should have femoral arterial and venous 4 Fr sheaths placed in anticipation of ECMO. Transferring to tertiary facilities capable of ECMO may require early decision-making and awareness of local capabilities.[7] Anticoagulation-free ECMO should be considered if ongoing bleeding or DIC is present.[23] Postpartum Management

Extracorporeal membrane oxygenation (ECMO) life support has proven successful for refractory cardiogenic shock secondary to AFE when severe right ventricular dysfunction does not respond to medical management.[23] ECMO provides respiratory and hemodynamic support through the femoral vasculature until the right ventricle's function improves. Any patient persisting in cardiopulmonary collapse should have femoral arterial and venous 4 Fr sheaths placed in anticipation of ECMO. Transferring to tertiary facilities capable of ECMO may require early decision-making and awareness of local capabilities.[7] Anticoagulation-free ECMO should be considered if ongoing bleeding or DIC is present.[23] Postpartum Management Following fetal delivery, managing hemorrhage, uterine atony, and the resulting coagulopathy (ie, DIC) is the next step.[24] Empirical administration of packed red blood cells (pRBCs), fresh frozen plasma (FFP), and platelets in a 1:1:1 ratio has been the traditional approach. However, cryoprecipitate is preferred over FFP to reduce volume overload, given its concentrated clotting factors, including factor VIII, von Willebrand factor, and fibrinogen. Tranexamic acid may be administered for fibrinolysis.[25] Blood products are used for fluid resuscitation to mitigate the risk of volume overload.[23] Investigational Therapies While investigational, anecdotal reports in the literature cite the use of several other medications, including rivaroxaban (a factor Xa inhibitor), C1 esterase inhibitor concentrate, ketorolac, ondansetron, and aminocaproic acid.[23] Debriefing Procedure Debriefing is recommended to review processes, identify areas for improvement, and provide emotional support to patients, families, and clinicians. Reporting all cases of AFE to the international AFE registry contributes to improving outcomes in future situations. Simulations and drills are valuable in preparing the care team for these unusual yet emergent clinical situations.[23]

AFE is prone to misdiagnosis, prompting ongoing efforts to clarify its etiology, risk factors, and pathogenesis.[8] Vigilance must be taken for potentially reversible causes, including hypovolemia, hypoxemia, and hypothermia. Consideration of underlying reversible diagnoses, eg, myocardial infarction or tamponade, acidosis, hyperkalemia, and tension pneumothorax, is warranted.[23] The differential diagnosis for a pregnant patient experiencing complete cardiovascular collapse during or around the time of delivery, followed by significant hemorrhage, should encompass the following: Pulmonary embolism Peripartum cardiomyopathy Septic shock Aortic dissection Magnesium toxicity [23] Air or cholesterol embolism Myocardial infarction Venous air embolism Eclampsia Aspiration Toxic reaction to anesthetic medications Anaphylaxis Obstetrical hemorrhage causing coagulopathy and shock Cephalad spread of spinal anesthetic [23][4][23] AFE exhibits some similarities to pulmonary embolus but lacks the ongoing coagulopathy seen in pulmonary embolism. Postpartum cardiomyopathy would likely manifest significant ST-T wave changes on electrocardiography, accompanied by predominant symptoms of left-sided congestive heart failure. Bedside echocardiography (TEE or TTE) can aid in distinguishing AFE with its classic right ventricular dilatation, overload pattern, and septal bowing into the left ventricle. Septic shock typically presents with the classic systemic inflammatory response syndrome (SIRS) picture and is unlikely to lead to sudden cardiovascular collapse. Myocardial infarction, unless antecedent to the cardiac arrest, would display typical ST-T wave changes and elevated serial cardiac enzymes, observable through bedside echocardiography. Venous air embolism usually presents with wheezing, gasping, and chest pain before cardiovascular collapse. Eclampsia may be suggested by hypertension, edema, proteinuria, headaches, or seizures preceding the collapse. Anaphylaxis should exhibit premonitory symptoms, eg, wheezing, dyspnea, rash, urticaria, and hypotension before cardiovascular decompensation. Cephalad distribution of spinal anesthetic would present with an elevated sensory level, weakness of the upper extremities, difficulty in speaking, dysphagia, and bradycardia.[23]

AFE stands as a prominent cause of maternal mortality in developed countries, with a historical mortality rate initially reported at 61%, but recent data suggests a lower rate of around 10%.[23] Early and effective management of cardiac arrest significantly enhances survival, with a case fatality rate ranging between 11% to 26% in developed nations.[23] Tragically, within the first hour following an AFE, an estimated 50% of patients succumb, and two-thirds face mortality within 5 hours. The peak period of death has been noted to be 1 to 12 hours after the AFE occurs.[3] A California-based study indicated that 26.4% of affected pregnant patients died, while 66% developed DIC.[23] Maternal survival remains uncommon, but prompt recognition and resuscitation improve prognoses. The United Kingdom AFE registry reported a 37% mortality rate, with 7% of survivors experiencing neurological impairment.[23] Survivors of AFE often grapple with substantial neurological, pulmonary, and cardiovascular deficits, affecting two-thirds of these recently pregnant patients. Recurrence risks are uncertain, but instances of successful subsequent pregnancies have been documented.[23] Elective cesarean delivery recommendations for future pregnancies to mitigate labor-related risks are contentious. Infant mortality rates hover around 30%, accompanied by elevated risks of hypoxic-ischemic encephalopathy, cerebral palsy, and cognitive disabilities among survivors. The grim statistics extend to stillbirth and neonatal death, reaching rates as high as 10% to 40%. Patients who survive pregnancies complicated by AFE commonly grapple with depression and post-traumatic stress disorder (PTSD).[23] While initial rates of neurologically intact survival were reported at 15%, recent data suggest an improvement, with estimates nearing 46%. Advances in diagnosis, medical management, and a deeper understanding of AFE's pathophysiology have contributed to improved survival rates. Early recognition has not only improved maternal outcomes but also reduced neonatal mortality and morbidity rates.[23]

Survivors of AFE may contend with a spectrum of significant complications, including the following: Renal failure Cardiac failure Prolonged respiratory failure leading to adult respiratory distress Myocardial infarction Arrhythmias Cardiomyopathy Congestive heart failure Left ventricular systolic dysfunction Prolonged coagulopathy Respiratory failure (extended) Prolonged bronchospasm Liver failure Cardiogenic pulmonary edema Seizures Anoxic encephalopathy Various cognitive or neurologic impairments Infants delivered emergently during maternal AFE are at heightened risk for sustaining hypoxic-ischemic encephalopathy. This often results in a significantly cognitively impaired child, potentially manifesting chronic epilepsy, motor impairment, and developmental delay.[23][3]

AFE is an exceptionally severe condition characterized by its sudden onset, and unfortunately, its occurrence is largely unpredictable. Despite its unforeseeable nature, there are limited preventive measures that can be taken. To minimize the risk of AFE, care should be exercised during certain maneuvers, eg, the insertion of a pressure catheter and intraamniotic infusion therapy. Additionally, efforts should be made to refrain from incising the placenta during cesarean delivery whenever possible.[16] Future studies are crucial to identifying individuals at the highest risk, as long-term mental and physical health consequences are prevalent in these patients. Notably, only around 60% of women affected by AFE manage to return to their previous state of well-being. Further research can contribute to a better understanding of risk factors and improve preventive strategies.

AFE represents a rare but catastrophic obstetric emergency characterized by sudden cardiorespiratory collapse, disseminated intravascular coagulation, and multisystem organ dysfunction. Triggered by the entry of amniotic fluid and fetal components into the maternal circulation, AFE initiates an anaphylactoid immune response that produces pulmonary vasoconstriction, right heart failure, and profound coagulopathy. Clinical presentation develops abruptly, often with hypoxia, hypotension, neurologic changes, seizures, and hemorrhage. Survivors frequently experience long-term cardiac, renal, neurologic, and pulmonary complications. Diagnosis relies on exclusionary criteria, clinical suspicion, and recognition of predisposing factors, including advanced maternal age, grand multiparity, placenta accreta spectrum disorder, polyhydramnios, multiple gestation, operative delivery, and prior allergies. Immediate, evidence-based interprofessional intervention is essential to reduce maternal and fetal morbidity and mortality.[16] Effective management of AFE requires rapid coordination among physicians, general practitioners, advanced practitioners, nurses, pharmacists, and other health professionals. Clinicians, including obstetricians, anesthesiologists, and neonatologists, must apply advanced resuscitation skills, manage right ventricular failure, optimize coagulopathy management, and implement massive transfusion protocols. Pharmacists ensure the timely availability of blood products and hemostatic agents, while nurses provide continuous bedside monitoring, airway support, and procedural assistance. Interprofessional communication and collaboration allow synchronized execution of resuscitative hysterotomy, extracorporeal membrane oxygenation, and ongoing maternal and neonatal care. Strategic use of simulation, structured debriefing, and adherence to standardized protocols enhances team performance, patient safety, and overall outcomes in this high-acuity obstetric emergency.