Amniotic Fluid Embolism

Amniotic fluid embolism (AFE) is a rare, catastrophic obstetric emergency. It presents as sudden cardiovascular collapse and/or respiratory compromise during labor, delivery, or within 48 hours postpartum.

Diagnosis is clinical and one of exclusion. There is no specific premorbid diagnostic test. Definitive diagnosis in non-survivors is established at autopsy.

History

• First described in 1926
• Widely recognized following a 1941 autopsy series

Epidemiology

• Incidence: 1–12 cases per 100,000 deliveries
• Mortality: Up to 80%

Pathophysiology

Amniotic fluid likely enters the maternal circulation via:

• Endocervical veins
• Placental insertion site
• Uterine trauma

Systemic effects include:

1. Cardiogenic Shock:
   • Due to pulmonary vasospasm, RV failure, LV hypoxia, or myocardial depression
2. Respiratory Failure:
   • V/Q mismatch
   • ARDS-type non-cardiogenic pulmonary edema
   • Cardiogenic pulmonary edema (severe LVF)
3. Anaphylactoid/Inflammatory Reaction:
   • Immune response to fetal antigens
   • May explain symptom delay after fluid entry

Risk Factors

• Precipitous labor
• Advanced maternal age
• Cesarean or instrumental delivery
• Placenta previa or abruption
• Grand multiparity
• Uterine or cervical laceration
• Eclampsia
• Fetal distress
• Medically induced labor

These factors are associated but not predictive—AFE is considered unpredictable and unpreventable.

Clinical Features

Suspect AFE when sudden onset of:

• Hypotension/cardiogenic shock
• Hypoxemia/respiratory failure
• Coma or seizures
• Coagulopathy (DIC and hemorrhage)

Timing: Most cases occur during labor or within hours postpartum, but may present up to 48 hours after cesarean delivery.

Partial syndrome: May involve only respiratory impairment and DIC

Differential Diagnosis

• Pulmonary embolism
• Anaphylaxis
• Septic shock
• Eclampsia
• Peripartum cardiomyopathy
• Myocardial infarction
• Air embolism
• Anesthetic complications (e.g., high spinal)
• Massive aspiration
• Transfusion reaction

Investigations

No specific diagnostic test—focus on ruling out other causes and assessing severity.

Laboratory Tests:

• FBE
• U&Es, glucose
• LFTs
• Coagulation profile (e.g., ↓platelets, ↑PT/APTT, ↓fibrinogen, ↑D-dimers)
• ABG/VBG/lactate

Other:

• 12-lead ECG
• Chest X-ray

Emerging tests (not yet validated):

• TKH-2 antigen
• Insulin-like growth factor binding protein-1

Management

There is no specific treatment—supportive management is the cornerstone.

1. Resuscitation (ABCs)

• 100% oxygen
• Intubation and ventilation if needed
• IV fluid resuscitation

2. Monitoring

• Arterial line
• Central venous catheter
• Indwelling catheter
• Continuous ECG

3. Inotropes

• Vasopressors (e.g., norepinephrine) as needed for hypotension

4. Seizure Management

• IV benzodiazepines

5. Coagulopathy

• FFP, platelets, cryoprecipitate (for fibrinogen replacement)

6. Hemorrhage Control

• Transfusion as needed
• Hysterectomy for uncontrolled uterine bleeding/atony

7. Urgent Delivery

Required in:

• Fetal distress
• Rapid maternal deterioration
• Potential maternal benefit from delivery

Methods:

• Operative vaginal delivery (if fully dilated, station ≥+2)
• Emergency cesarean otherwise

Disposition

Immediate referral to:

• Obstetrics
• Anaesthetics
• ICU
• Paediatrics (if fetus undelivered)

Prognosis

• Maternal mortality: Up to 80%
• Neurological sequelae common among survivors
• Neonatal mortality is high but may be improved with timely maternal support and delivery

US Registry (1995):

• 61% maternal mortality
• Only 15% survived neurologically intact

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References

History

• Meyer JR. Embolia pulmonar amnio caseosa. Brasil-Medico 1926; 40: 301–303
• Steiner PE, Lushbaugh CC. Landmark article, Oct. 1941: Maternal pulmonary embolism by amniotic fluid as a cause of obstetric shock and unexpected deaths in obstetrics. By Paul E. Steiner and C. C. Lushbaugh. JAMA. 1986 Apr 25;255(16):2187-203.

FOAMed

• Nickson C. Amniotic Fluid Embolism (AFE). CCC

Publications

• Benson MD. Amniotic fluid embolism: the known and not known. Obstet Med. 2014 Mar;7(1):17-21.
• Rafael A, Benson MD. Amniotic fluid embolism: Then and now. Obstet Med. 2014 Mar;7(1):34-6. 
• McDonnell, N., Knight, M., Peek, M.J. et al. Amniotic fluid embolism: an Australian-New Zealand population-based study. BMC Pregnancy Childbirth 15, 352 (2015).
• Kaur K, Bhardwaj M, Kumar P, Singhal S, Singh T, Hooda S. Amniotic fluid embolism. J Anaesthesiol Clin Pharmacol. 2016 Apr-Jun;32(2):153-9.