Amniotic fluid embolism: a review of 10 fatal cases.

A study of 10 fatal cases of amniotic fluid embolism, confirmed by autopsy and post-mortem histological examination, that occurred in Singapore between 1983-1992, showed that the majority (9 cases) were multiparous, with between 2-4 previous normal pregnancies each. Seven had uneventful antenatal histories. In all cases, the clinical onset was sudden and unexpected, having occurred during the first stage of labour in 8 subjects and being associated with convulsions in 5. There were seven cases of coagulopathy, with 6 of disseminated intravascular coagulation. Overall, foetal survival was poor. Three cases were associated with induction of labour, while another 3 occurred after augmentation. Emergency caesarean sections were performed in 5 cases. Autopsy demonstrated moderate to severe pulmonary oedema in 9 cases, accompanied by pulmonary haemorrhage in 6. Mild coronary atheroma was present in 6 cases, with 3 showing subendocardial haemorrhage. Significant utero-cervical ruptures or lacerations were found in 3 cases. Microscopy demonstrated the presence of squamous epithelial emboli within the pulmonary vasculature in all cases. Other histological features included fibrin microthrombi (3 cases), alveolar and pulmonary interstitial inflammation, focal myocardial and hepatocellular necrosis, and myocardial interstitial inflammation. Although the precise pathogenesis of amniotic fluid embolism has remained somewhat enigmatic, recent evidence points towards a combination of a severe haemodynamic disturbance followed by secondary coagulopathy in about 40% of patients who survive the initial event. Leucotrienes, prostaglandins and other vasoactive substances contained in amniotic fluid are postulated to play a fundamental role in its pathogenesis. Amniotic fluid is also thought to possess thromboplastin-like properties.(ABSTRACT TRUNCATED AT 250 WORDS)