Pathophysiology of amniotic fluid embolism is best described as which statement?

• A. It is an abnormal maternal inflammatory response to fetal antigens in amniotic fluid
• B. It is primarily an embolic obstruction of pulmonary vessels
• C. It is caused by rupture of the umbilical vein
• D. It is due to placental abruption

Answer: (A)

Amniotic fluid embolism is best understood as an abnormal maternal inflammatory/immune response to fetal antigens contained in amniotic fluid that reach the mother’s circulation. This triggers a massive mediator release, producing a systemic inflammatory/vasoactive cascade that leads to abrupt respiratory distress, cardiovascular collapse, and often disseminated intravascular coagulation. The emphasis is on the inflammatory reaction to fetal components rather than a simple physical blockage of the pulmonary vessels.

This explains why it’s not described best as a straightforward embolic obstruction of the lungs. While embolic blood flow issues can occur, the hallmark is the intense inflammatory response and coagulopathy that drive the clinical picture. It also isn’t caused by rupture of the umbilical vein or by placental abruption, which are separate obstetric events with different pathophysiologies.