Anesthesiology APPLIED Exam › Obstetric anesthesia

Amniotic fluid embolism

Obstetric anesthesia·~5 min read· Physician-reviewed✓ Sourced · 4

Stem

A 36-year-old woman, 88 kg, G3P2 at 39 weeks, is in oxytocin-augmented labor with a working lumbar epidural that was last bolused 90 minutes ago. Minutes after artificial rupture of membranes she says something is wrong, becomes agitated and cyanotic, and loses consciousness. SpO2 is 81%, blood pressure 64/30 mmHg, heart rate 132, and the fetal heart rate has fallen to 70 bpm.

Question

What do you think is happening, and how will you manage her?

Ideal answer

HeadlineSudden hypoxia and hypotension in labor is amniotic fluid embolism until proven otherwise; I treat without waiting, because no test confirms it.¹ I call an obstetric code.

Neonatal team; oxytocin off; left uterine displacement. So resuscitation and delivery run side by side.
100% oxygen and early rapid sequence intubation. Her saturation will not hold; large-bore access above the diaphragm and an arterial line.
Pulseless: compressions, ACLS, unchanged drug doses, scalpel ready. With a fetus of 23 weeks or more, SMFM recommends immediate delivery: incision by 4 minutes, delivery by 5.¹^,2
With a pulse, treat right ventricular failure. Norepinephrine for pressure, dobutamine or milrinone for contractility, inhaled nitric oxide for pulmonary vasoconstriction; no large fluid boluses distending it.¹
CBC, fibrinogen, coagulation now; massive transfusion early. DIC follows in most cases.¹

Watch for: a dilated, hypokinetic right ventricle on bedside echo, which supports the diagnosis.

Breaking down the answer

Clinical diagnosis — SMFM recommends considering AFE in any sudden cardiorespiratory collapse in labor or just after delivery; it remains a clinical diagnosis.¹ Saying "I treat before I confirm" shows judgment.
Delivery is resuscitation — the 2025 AHA update renames perimortem cesarean "resuscitative delivery" and keeps the 5-minute goal.¹^,3
The right ventricle fails first — the early phase is acute cor pulmonale; hypoxia, hypercapnia and acidosis raise pulmonary vascular resistance, so ventilation and oxygenation are hemodynamic therapy. Left ventricular failure with pulmonary edema follows minutes to hours later.¹
Plan the coagulopathy before it arrives — DIC can appear immediately or later; products should not wait for laboratory results; SMFM describes 1:1:1 hemostatic resuscitation, and AHA 2025 adds balanced massive transfusion for suspected life-threatening AFE.¹^,3
Keep a working differential — her epidural makes high block and local anesthetic toxicity real possibilities, since both cause collapse; PE, MI, anaphylaxis, eclampsia and hemorrhage. Right ventricular dysfunction on echo favors AFE over most mimics.¹
ECMO is a rescue, not a routine — SMFM calls it controversial because anticoagulation worsens bleeding; AHA 2025 now calls ECPR reasonable for pregnant patients not responding to standard resuscitation.¹^,3

Follow-up question

She is delivered by cesarean at 4 minutes and has return of circulation. Twenty minutes later she is oozing from every IV site and the incision, the uterus is boggy, and the fibrinogen returns at 90 mg/dL. What now?

Follow-up answer

HeadlineConsumptive coagulopathy from AFE, worsened by atony; I tell the surgeon and blood bank we are in massive transfusion.

Red cells, plasma and platelets in a balanced ratio, keeping platelets above 50,000 and the PT and PTT near normal;¹ cryoprecipitate for the fibrinogen. Oxytocin and second-line uterotonics, and tranexamic acid if viscoelastic testing shows hyperfibrinolysis.¹ If bleeding continues, the surgeon packs the pelvis rather than chasing every vessel. Recombinant factor VIIa only as a last resort, because of thrombosis risk.¹ Labs every 30 minutes, then ICU with a MAP target of 65 mmHg and SpO2 of 94–98%.¹

Pitfalls that cost points

Moving an arrested patient to the operating room for delivery instead of delivering where she is.
Calling atony with dilutional coagulopathy AFE; SMFM names that as a common diagnostic error.¹

Rapid-fire

Q: What is the classic triad? A: Sudden hypoxia and hypotension, followed in many cases by coagulopathy, in relation to labor and delivery.¹

Q: What are the research criteria? A: Sudden arrest or hypotension with respiratory compromise, overt DIC before enough blood loss to explain it, onset in labor or within 30 minutes of placental delivery, and no fever in labor.⁴

Q: Is atropine, ondansetron and ketorolac recommended? A: No; it appears in case reports, but a 2025 review advises against it given limited evidence and the risk of worsening bleeding.⁴

Q: Do steroids help? A: No evidence supports their routine use.¹

Q: What about future pregnancies? A: No recurrences have been reported in subsequent pregnancies, but the numbers are too small to be definitive.¹

Numbers to know

Item	Value
Incidence	~1.9–6.1 per 100,000 births⁴
Mortality	20–60%, depending on criteria⁴
Immediate delivery after arrest	Fetus 23 weeks or more¹
Resuscitative delivery	Incision by 4 min, delivery by 5 min²
Dobutamine / milrinone	2.5–5 mcg/kg/min / 0.25–0.75 mcg/kg/min¹
Inhaled nitric oxide	5–40 ppm¹
Platelet target in DIC	Above 50,000¹

Sources

1.SMFM Clinical Guideline #9: Amniotic fluid embolism: diagnosis and management · SMFM (Pacheco et al., Am J Obstet Gynecol), 2016 · assets.noviams.comSeven GRADE recommendations; Table 2 right-ventricular failure drug doses; post-arrest targets.
2.SOAP Consensus Statement on the Management of Cardiac Arrest in Pregnancy · SOAP (Lipman et al., Anesth Analg), 2014 · soap.org
3.Highlights of the 2025 AHA Guidelines for CPR and ECC · AHA, 2025 · cpr.heart.orgSpecial circumstances: ECPR in pregnancy; balanced massive transfusion for suspected life-threatening AFE.
4.Amniotic Fluid Embolism (AFE) · The ObG Project, 2025 · obgproject.comSummarizes Pacheco 2020 (incidence), Clark 2014 (mortality), the 2016 SMFM/AFE Foundation research criteria, and Pacheco 2025 on atropine-ondansetron-ketorolac.

Facts on this page were checked against these sources on Oct 15, 2026. Guidelines change; confirm doses against current institutional protocols.