Amniotic fluid embolism — FFICM MCQ

Correct answer: A — Amniotic fluid embolism

The correct answer is A, Amniotic fluid embolism. The triad of sudden hypoxaemia and cardiovascular collapse in labour, followed by acute severe coagulopathy and right ventricular dysfunction on echo, is the classic UKOSS clinical diagnostic pattern for AFE: acute hypotension or cardiac arrest, acute hypoxia, and coagulopathy occurring in the absence of any other explanation. The mechanism is an anaphylactoid-type reaction to fetal antigens entering the maternal circulation, causing pulmonary vasospasm, acute RV strain, and consumptive coagulopathy with uterine bleeding as a secondary consequence rather than the primary insult. The absence of preceding fever excludes sepsis and the absence of major haemorrhage before collapse excludes atony-driven shock as the initiating event, leaving AFE as the unifying diagnosis explaining the cardiorespiratory, coagulation and echocardiographic findings together. Why the other options are wrong: D. Pulmonary aspiration alone: causes hypoxaemia and possible bronchospasm but does not explain the abrupt severe coagulopathy or RV dysfunction seen here. B. Uterine atony as primary event: atony produces haemorrhage as the initiating problem, whereas here bleeding and coagulopathy developed only after the hypoxaemic collapse and arrest. C. Epidural high block alone: causes hypotension and respiratory compromise from motor and sympathetic blockade but has no mechanism for triggering DIC or RV failure. E. Tension pneumothorax: would explain hypoxaemia and hypotension via impaired venous return, but there is no clinical link to coagulopathy or uterine bleeding, and no risk factors (trauma, ventilation) are given. Key point: Sudden peripartum collapse with hypoxaemia, cardiovascular shock and early severe coagulopathy (with RV strain on echo) without a preceding septic or haemorrhagic trigger is the hallmark of amniotic fluid embolism, a clinical diagnosis of exclusion.

Reference: UKOSS (National Perinatal Epidemiology Unit, Oxford), Amniotic Fluid Embolism surveillance clinical case definition, https://www.npeu.ox.ac.uk/ukoss/current-surveillance/amf