An Overview of Amniotic Fluid Embolism: Past, Present and Future Directions

Abstract

Objective: A recent report has highlighted that amniotic fluid embolism (AFE) is the first among maternal mor- tality in Japan. The clinical presentation is not the same with respect to symptoms, timing and subsequent course. Methods: This article reviews the English language literature for pathophysiology on AFE based on the clinical and ani- mal studies. Results: First, AFE syndrome may be divided into three subgroups designated the classical subtype, the anaphylactoid subtype and the DIC subtype, each having a distinct pattern of clinical symptoms and disease severity. Second, AFE- associated reactions can be classified as an anaphylactoid reaction or complement activation to fetal antigens or an idio- syncratic reaction. Host idiosyncrasy may be a major cause of hypersensitivity reaction. Third, the AFE reaction may be caused by a combination of immunologic and vasospastic factors. Finally, the development of effective markers for diag- nosing entry of amniotic fluid into the maternal circulation would have an impact on early diagnosis and AFE-related mortality. Conclusion: This review summarizes new insights into the pathophysiology of AFE, with a focus on the potential direc- tion of future research. Keyword: Amniotic fluid embolism, Anaphylactoid, Hypersensitivity, Meconium, Vasospasm.