Prevalence of Amniotic Fluid Embolism
Amniotic fluid embolism is a rare obstetric catastrophe occurring in approximately 2 to 8 per 100,000 deliveries, though estimates vary widely due to lack of international consensus on diagnostic criteria. 1, 2
Incidence Estimates
The reported incidence of AFE varies considerably across different studies and populations:
- Most recent population-based data indicates an incidence of 7.7 per 100,000 births in the United States based on analysis of 3 million deliveries 3
- European data reports approximately 2 to 2.5 cases per 100,000 maternities 4
- Historical estimates have ranged from 1 in 8,000 to 1 in 80,000 pregnancies, reflecting the diagnostic challenges and varying case definitions 5, 6
Why Prevalence Estimates Vary
The wide variation in reported incidence stems from several critical factors:
- No international consensus exists on diagnostic criteria, making standardized reporting across regions and institutions difficult 1
- AFE is a clinical diagnosis of exclusion with no confirmatory laboratory or imaging test, leading to both underdiagnosis of mild cases and potential overdiagnosis when other causes are not adequately excluded 7, 8
- Improved critical care recognition has identified more atypical or milder cases in recent decades, potentially increasing reported incidence while simultaneously decreasing mortality 7
Mortality Burden
Despite its rarity, AFE carries devastating consequences:
- Case fatality rates range from 13% to 44% in recent prospective studies, with older literature reporting mortality as high as 80% 4, 2, 3
- AFE remains one of the leading causes of direct maternal death in high-income countries 4
- The mortality rate is 21.6% based on the largest U.S. population-based cohort study 3
Clinical Context
While the absolute number of AFE cases is small, both maternal and perinatal morbidity and mortality remain significant even with ideal management 1. The condition warrants high clinical suspicion in any pregnant or immediately postpartum woman presenting with sudden cardiovascular collapse, respiratory distress, or unexplained coagulopathy 1, 7.