Amniotic Fluid Embolism (AFE) image

Amniotic Fluid Embolism (AFE)


  • Amniotic fluid embolism (AFE) is a rare cause of maternal collapse during or immediately after delivery, seen in approximately 1.9 to 6.1 per 100,000 births (Pacheco et al. AJOG, 2020)
  • Mortality estimates for AFE range from 20% to 60% depending on the diagnostic criteria used, however when cardiac arrest occurs, survival rates are much lower (Clark. Obstet Gynecol, 2014)
  • Diagnosis
    • Classic diagnostic triad occurring in labor, at, or immediately after, delivery
      • Sudden hypoxia | Hypotension | Coagulopathy
  • Right ventricular strain or failure due to pulmonary vasoconstriction may be seen
    • Often evident on transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) once circulation returns (Pacheco et al. AJOG, 2020)
  • Management protocols based on expert opinion due to limited published data with focus on 
    • Team training |Simulation |Coordination
    • Outcomes appear to be improved if obstetrician and anesthesiologist are present (Fitzpatrick et al. PLoS Medicine, 2019)   



  • “Maternal shock” from presumed embolism of amniotic fluid was first described in a case series in 1941, and this etiology was unchallenged for many years
    • The findings in this series have since been disproved, however the name of “AFE” has continued in use
  • AFE is an abnormal activation of the pro-inflammatory mediator systems in response to release of fetal tissue in maternal circulation (Clark. Obstet Gynecol, 2014)
    • Transient but profound systemic and pulmonary hypertension can lead to maternal cardiac arrest
    • Arrest is often followed by DIC
    • Cause of DIC unknown | Because DIC is also seen in cases of placental pathology (e.g., abruption and accreta), placental etiology may be an underlying mechanism   

Diagnosis of AFE

Clark Criteria

Developed under the auspices of the “M in Maternal-Fetal Medicine Committee” of the Society for Maternal-Fetal Medicine and the Amniotic Fluid Embolism Foundation (Clark et al. AJOG, 2016) 

  • Sudden onset of cardiorespiratory arrest, or both hypotension (systolic blood pressure <90 mm Hg) and respiratory compromise (dyspnea, cyanosis, or peripheral capillary oxygen saturation [SpO2] <90%)
  • Coagulopathy must be detected prior to loss of sufficient blood to itself account for dilutional or shock-related consumptive coagulopathy
  • Clinical onset during labor or within 30 min of delivery of placenta
  • No fever (≥38.0°C) during labor
  • DIC: Based on the International Society on Thrombosis and Haemostasis (ISTH) DIC score (modified for pregnancy) | Score ≥3 using the is following scoring system is compatible with overt DIC in pregnancy
    • Platelet count
      • >100,000/mL = 0
      • <100,000/mL = 1
      • <50,000/mL = 2
    • Prolonged PT or INR
      • <25% increase = 0
      • 25-50% increase = 1
      • >50% increase = 2
    • Fibrinogen level
      • >200 mg/L = 0
      • <200 mg/L = 1


  • First response: Effective maternal CPR per ACLS protocol (see related OBG L&D Maternal Cardiac Arrest chapter)
  • Once patient is stabilized
    • TTE or TEE (if appropriately trained personnel are available) to diagnose right heart strain or failure
  • Management can be tailored to include
    • Limits on fluid bolus
    • Ventilator adjustments to prevent further pulmonary hypertension
    • Medications for right heart failure
  • If DIC occurs
    • Initiate massive transfusion protocol (see ‘Related Topics’ below)
    • Higher dose (2g) vs lower dose of tranexamic acid (TXA) may improve maternal outcome (Fitzpatrick et al. PLoS Medicine, 2019)
  • Role of ECMO
    • There are case reports of ECMO being used as an adjunct to provide ventilatory support
  • Women who experience cardiac arrest and multiorgan failure – including acute lung injury and or ischemic brain injury – often have a longer, more complex recovery 
  • Acute management protocols are based on expert opinion and case reports
    • See primary sources below for two regimens

Differential Diagnosis

SMFM notes that while the following may be included in the differential diagnosis depending on signs and symptoms, “Bedside echocardiography demonstrating right ventricular dysfunction favors the diagnosis of amniotic fluid embolism”

  • Cardiac: Myocardial infarction | Cardiogenic shock | Peripartum Cardiomyopathy
    • Look for risk factors such as diabetes, smoking, obesity, dyslipidemia, history of CAD
    • Cardiac troponins and 12 lead ECG can help with diagnosis
    • Echocardiogram to assess patient for dilated cardiomyopathy
  • Pulmonary embolism
    • CT angiography or ventilation perfusion scan
    • Thromboembolism not generally associated with DIC
  • Anesthesia complication
    • High spinal: Apnea but not usually associated with cardiovascular collapse 
    • Intravascular injections of local anesthetic: Timing of collapse usually related temporally to injection
  • Air embolism
    • Venous or atrial (latter associated with neurologic findings)
  • Eclampsia
    • Association with seizures
    • DIC and cardiovascular collapse not commonly seen
  • Anaphylactic shock
    • Symptoms include urticarial rash and bronchospasm (bronchospasm may infrequently occur in AFE)  
    • Temporally related to medication administration
    • Right heart failure and DIC are usually not associated with anaphylaxis


Pacheco et al. AJOG, 2020

  • In this clinical expert article, the authors review etiology of AFE and propose a treatment pathway | They acknowledge that there are no studies of treatment regimens
  • The following proposed treatment plan is based on their critical care expertise
    • Start high quality CPR
    • Defibrillate as needed
    • Prepare for operative delivery or early perimortem delivery
    • Early TTE after return of circulation | Do not interrupt compressions for TTE
  • Evidence of right heart strain (Cor Pulmonale)
    • Vasopressors
    • Inotropes
    • Pulmonary vasodilators
    • Avoid fluid bolus
  • Evidence of DIC
    • Activate mass transfusion protocol | Transfuse at 1:1:1 PRBCs/FFP/Plt
    • Uterotonics as needed to control bleeding
  • If persistent hemodynamic instability: Consider ECMO

Rezai et al. Case Reports in Obstetrics and Gynecology, 2017

  • Case report of AFE managed with a novel regimen, entitled ‘A-OK’ | Paper includes literature review of previous use of this protocol
  • In their case report, instituting this protocol at the time of maternal collapse resulted in recovery of blood pressure and oxygenation within 2 to 3 minutes 
  • The protocol is meant to address the underlying pathophysiology of the collapse
    • Atropine (0.2mg): Counteracts vagal overstimulation | Improves vasomotor tone
    • Ondansetron (8mg): Blocks serotonin receptors inhibiting release of further mediators
    • Ketorolac (15mg): Blocks thromboxane production preventing coagulopathy
  • This protocol is not widely incorporated into expert opinion at this time



  • Open access document provides an outline of diagnosis and management for AFE, including medication selection and dosing for management of right heart failure
  • Key recommendations for post-arrest management include
    • Use of fluids, vasopressors, and inotropes | Goal is to maintain a mean arterial blood pressure of 65 mmHg
    • Treat fever aggressively: Fever may worsen ischemia-reperfusion injury to the brain
  • Avoid administration of 100% oxygen after survival of cardiac arrest | Hyperoxia will also worsen ischemia-reperfusion injury, and
  • Wean inspired oxygen fraction to maintain a pulse oxymetry value of 94% to 98%
  • Maintain serum glucose levels between 140 to 180 mg/dL | Use IV insulin infusions as needed

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Clinical Expert Series: Amniotic Fluid Emoblism (Clark. Obstet Gynecol, 2014)

Amniotic fluid embolism: principles of early clinical management (Pacheco et al. AJOG, 2020)

Atypical Amniotic Fluid Embolism Managed with a Novel Therapeutic Regimen (Rezai et al. Case Reports in Obstetrics and Gynecology, 2017)

SMFM: Amniotic Fluid Embolism: Diagnosis and Management

Risk factors, management, and outcomes of amniotic fluid embolism: A multicountry, population-based cohort and nested case-control study (Fitzpatrick et al. PLoS Medicine, 2019)

Proposed diagnostic criteria for the case definition of amniotic fluid embolism in research studies (Clark et al. AJOG, 2016)