Abstract
Amniotic fluid embolus is the eighth most common cause of all maternal deaths, down one place from the previous edition of this book [2, 5]. At 0.35 per 100 000 maternities (95% CI 0.15–1.39) it has declined from the fourth to the fifth leading cause of direct maternal deaths in the United Kingdom. Maternal case fatality rates are between 11% and 32% in the United Kingdom, Australia and the United States [9, 4, ref surveillance]. There is a fall in case mortality rates which is probably due to high-level supportive care and diagnosis of milder cases [6].
Women who died or who had permanent neurological injury were more likely to present with cardiac arrest (83% vs. 33%, P < 0.001), be from ethnic-minority groups (adjusted odds ratio [AOR] 2.85; 95% CI 1.02–8.00), to have had a hysterectomy (OR 2.49; 95% CI 1.02–6.06) and were less likely to receive cryoprecipitate (OR 0.30; 95% CI 0.11–0.80) [1].
Key Facts
Definition Amniotic fluid embolus (AFE) is a rare obstetric condition that is characterised by one or more of the following features, in the absence of any other clear cause:
Acute fetal compromise
Cardiac arrhythmias or arrest
Coagulopathy
Convulsion
Hypotension
Maternal haemorrhage
Premonitory symptoms, e.g. restlessness, numbness, agitation, tingling
Shortness of breath
Excluding women with maternal haemorrhage as the first presenting feature in whom there was no evidence of early coagulopathy or cardiorespiratory compromise [1]
Histological amniotic fluid embolus is the presence of fetal squames or hair in maternal lungs at postmortem [1].
Incidence There has been no change in incidence since 2010. It is approximately 2.0 per 100 000 deliveries (95% confidence interval [CI] 1.5–2.5) in the United Kingdom [2]. Similar incidences are found elsewhere, for example, 3.3 per 100 000 deliveries in Australia [3] and 6.0 per 100 000 singleton deliveries in Canada [4].
Morbidity and Mortality
Amniotic fluid embolus is the eighth most common cause of all maternal deaths, down one place from the previous edition of this book [2, 5]. At 0.35 per 100 000 maternities (95% CI 0.15–1.39) it has declined from the fourth to the fifth leading cause of direct maternal deaths in the United Kingdom. Maternal case fatality rates are between 11% and 32% in the United Kingdom, Australia and the United States [9, 4, ref surveillance]. There is a fall in case mortality rates which is probably due to high-level supportive care and diagnosis of milder cases [6].
Women who died or who had permanent neurological injury were more likely to present with cardiac arrest (83% vs. 33%, P < 0.001), be from ethnic-minority groups (adjusted odds ratio [AOR] 2.85; 95% CI 1.02–8.00), to have had a hysterectomy (OR 2.49; 95% CI 1.02–6.06) and were less likely to receive cryoprecipitate (OR 0.30; 95% CI 0.11–0.80) [1].
Key Implications
Maternal Pulmonary oedema, acute respiratory distress syndrome, disseminated intravascular coagulopathy (DIC), pulmonary embolus, haemorrhage, right and then left cardiac failure, cerebrovascular events, cardiorespiratory arrest, death
Fetal Fetal distress, hypoxic ischaemic encephalopathy (HIE), learning difficulties, cerebral palsy, intrauterine and neonatal death
Key Pointers
International variations exist in the definition of AFE [7], which may account for differences in incidence. Amniotic fluid embolus is sometimes considered in two phases. The first phase is characterised by an almost anaphylactoid reaction with hypotension and dyspnoea with or without cardiac arrest. The second phase is marked by haemorrhage and coagulopathy.
The following risk factors have been identified:
Maternal age greater than 35 years, (OR 9.85; 95% CI, 3.57–27.2)
Induction of labour (OR 3.86; 95% CI 2.04–7.31)
Multiple pregnancy (OR 10.9; 95% CI 2.81–42.7)
Caesarean delivery (OR 8.84; 95% CI 3.70–21.1)
Ethnic minority groups (OR 11.8; 95% CI 1.40–99.5)
Hyperstimulation remains heavily linked to AFE. In the last MBRRACE report of the nine women who died from an AFE, five were induced, among whom four deaths followed hyperstimulation [2].
Key Symptoms and Signs
Maternal
Fetal
Fetal distress, neonate with severe hypoxic ischaemic encephalopathy
Key Actions
Suspect a diagnosis of AFE in any woman during labour, after delivery or following surgical evacuation of the uterus with the following features [6]: maternal haemorrhage; hypotension; shortness of breath and new-onset respiratory symptoms; coagulopathy; premonitory symptoms such as restlessness, agitation, numbness, tingling; acute fetal compromise; cardiac arrest and/or arrhythmia; seizures.
A significant number of women present with maternal collapse. Therefore, management will consider this presentation foremost.
First-Line Management: Resuscitation
Call for Help – Early
Senior multidisciplinary involvement is important for a positive prognosis. The team should include obstetricians, anaesthetists, intensivists, haematologists and neonatologists.
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