Introduction Amniotic fluid embolism (AFE) is a rare but often lethal condition typically observed during labor or within 30 minutes postpartum, with an estimated incidence ranging from 1 in 8000 to 1 in 80000 deliveries. Specific risk factors for AFE might include advanced maternal age, placenta praevia, IVF pregnancies, fetal demise, preterm delivery and cesarean sections. Its pathophysiology, while not fully understood, is believed to involve vasospastic, inflammatory and immune reactions triggered by the presence of amniotic debris or other antigens in the maternal circulation. Young et al. recently proposed a new theory of pathophysiology with initial intravascular coagulation in the pulmonary circulation due to procoagulant surface antigen CD142 present in amniotic fluid, followed by derangements similar to any pulmonary embolism.

Clinical Presentation and Diagnosis AFE should be suspected intrapartum or in the immediate postpartum period in women experiencing sudden cardiovascular collapse, sudden respiratory distress and subsequent coagulopathy, particularly when no other explanations (such as postpartum haemmorhage, sepsis, pulmonary thromboembolism) are apparent. Clinical manifestations may include hypotension, arrhythmia, heart failure, shock, pulmonary edema, hypoxaemia, hemorrhagic coagulopathy, disseminated intravascular coagulopathy (DIC) and neurologic symptoms such as seizures or altered mental status. Identification of amniotic fluid debris in blood or lung tissue samples is not diagnostically useful.

Management Early recognition and prompt multidisciplinary care involving anaesthesiologists, obstetricians, neonatologists, critical care specialists and nurses is crucial for stabilizing patients and preventing further deterioration. Resuscitative efforts should be initiated concurrently with diagnostic evaluation to address cardiorespiratory compromise. Standard cardiac and respiratory life support measures, along with fluid resuscitation, vasopressor therapy, and transfusion of blood products, are essential components of initial management. Point-of-care testing, such as rotational thromboelastometry can be useful in diagnosing coagulopathy and guiding treatment, which might neccessitate use of fibrinogen and/or prothrombin complex. ECMO and cardipulmonary bypass should be considered when appropriate. The decision for immediate delivery should be made based on individual circumstances, with consideration given to fetal viability and maternal condition. For patients who stabilize following initial resuscitation or who present hemodynamically stable, supportive care focusing on airway management, hemodynamic stability, oxygenation, and prevention of bleeding is paramount. Further investigation should be performed to rule out alternative aetiologies.

Prognosis Despite improvements in management, AFE continues to carry significant maternal mortality and morbidity, with approximately 20% mortality rate and potential for neurologic sequelae in survivors due to cerebral hypoxia. Neonatal mortality rate is 20-25% and only 50% of the survivors may be neurologically intact.

References

1. Young BK, Florine Magdelijns P, Chervenak JL, Chan M. Amniotic fluid embolism: a reappraisal. Journal of Perinatal Medicine. 2023;52(2):126-135. doi:10.1515/jpm-2023-0365

2. Gist RS, Stafford IP, Leibowitz AB, Beilin Y. Amniotic fluid embolism. Anesthesia & Analgesia. 2009;108(5):1599-1602. doi:10.1213/ane.0b013e31819e43a4

3. Benson MD. Amniotic fluid embolism mortality rate. Journal of Obstetrics and Gynaecology Research. 2017;43(11):1714-1718. doi:10.1111/jog.13445

4. Loughran JA, Kitchen TL, Sindhakar S, Ashraf M, Awad M, Kealaher EJ. Rotational thromboelastometry (Rotem®)-guided diagnosis and management of amniotic fluid embolism. International Journal of Obstetric Anesthesia. 2019;38:127-130. doi:10.1016/j.ijoa.2018.09.001

5. Clark SL. Amniotic fluid embolism. Obstetrics & Gynecology. 2014;123(2):337-348. doi:10.1097/aog.0000000000000107

6. Clark SL, Romero R, Dildy GA, et al. Proposed diagnostic criteria for the case definition of amniotic fluid embolism in research studies. American Journal of Obstetrics and Gynecology. 2016;215(4):408-412. doi:10.1016/j.ajog.2016.06.037