Amniotic Fluid Embolism

Background

  • Obstetric emergency often presenting as sudden, profound and unexpected maternal collapse associated with hypotension, hypoxaemia and DIC
    • Majority die within an hour of symptom onset
    • Also a major cause of neonatal morbidity and mortality (high as 70%)
  • Caused by amniotic fluid/foetal cells enter the maternal circulation
  • Rare (between 1 in 8000 and 1 in 80000 pregnancies) but still accounts for ~5% of maternal deaths in the UK
  • Most occur during labour (70%); 19% in C-section and 11% following vaginal delivery (can also be caused by procedures such as amniocentesis, although this is actually a rare cause)

Risk factors

  • A few things seem to be associated (not proven)
    • Advanced maternal age
    • Multiparity
    • Meconium stained liquor
    • Intrauterine foetal death
    • Polyhydramnios
    • Strong, frequent or tetanic uterine contractions
    • Maternal history of allergy/atopy; chorioamnionitis; microsomia; uterine rupture and placenta accreta

Pathophysiology

  • Amniotic fluid increases the systemic and pulmonary resistance leading to acute pulmonary hypertension, with associated left ventricular failure and pulmonary oedema.
  • Accompanied by pulmonary vasospasm, hypoxia is often profound (may lead to ARDS)

Presentation

  • Maternal collapse, breathlessness, cyanosis, hypotension, dysrhythmias, DIC
    • May be preceded by foetal distress and sudden chills, shivering, sweating, anxiety, and coughing followed by signs of respiratory distress, shock, cardiovascular collapse, and convulsions
    • Other milder signs may include cough, headache, chest pain

Management

  • Often clinical diagnosis
  • Even where the diagnosis has not been confirmed- oxygen therapy, CPR if required and DELIVERY
    • Plasma transfusion may be appropriate

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