Amniotic fluid embolism (AFE) is a rare, potentially fatal, acute and unexpected birth complication that can affect both the mother and fetus. AFE occurs when amniotic fluid enters the maternal circulatory system and causes an allergic-like reaction (AFE Foundation 2023).
Defined as a two-phase response, AFE is characterised initially by rapid respiratory failure that can then progress to cardiac arrest. The second phase is the haemorrhagic phase, where the birthing parent experiences profuse bleeding at the wound site (usually the site of placental attachment or caesarean incision). Disseminated intravascular coagulopathy (DIC) (also known as consumptive coagulopathy) then develops, which prevents blood clotting. DIC requires urgent transfusions of blood and blood products (AFE Foundation 2023).
AFE typically presents during labour or around the time of delivery. Warning signs include a sudden onset of dyspnoea and hypotension, which is often followed by cardiovascular collapse and respiratory arrest. AFE has also been known to occur on rare occasions during first and second-trimester abortions, as late as 48 hours postpartum and following amniocentesis or uterine trauma.
AFE usually develops rapidly with early warning signs that could include:
(AFE Foundation 2023)
This may then lead to more serious symptoms, including:
(AFE Foundation 2023)
Diagnosis of AFE is usually made in the absence of other causes. In other words, it is a diagnosis of exclusion made only when all other possible clinical explanations for the symptoms have been ruled out (AFE Foundation 2023).
AFE was originally diagnosed only on post-mortem based on the presence of fetal material found in the vasculature of the lungs, but this is no longer considered a valid diagnostic method (AFE Foundation 2023).
Although there is still a great deal of uncertainty about the risk factors related to AFE, potential contributing factors may include:
(Haftel et al. 2024; AFE Foundation 2022; Moldenhauer 2024)
AFE is considered both unpredictable and unpreventable with an unknown cause, which makes risk assessment an almost impossible task. It can occur in healthy patients during labour, during caesarean section, after abnormal vaginal delivery or even during the second trimester of pregnancy (Haftel et al. 2024).
Given that AFE cannot be prevented or reversed, treatment of the birthing parent is entirely supportive, focusing on managing individual symptoms as they occur (Haftel et al. 2024).
Initial management should be based on the ABCs of adult life support, prioritising airway, breathing, and circulation (Haftel et al. 2024).
Urgent delivery of the fetus (resuscitative hysterotomy) may be required (Haftel et al. 2024).
AFE is the second most common direct cause of maternal death in Australia (AIHW 2023).
It’s estimated that mortality rate within the first hour after AFE is 50%. Unfortunately, those that survive often experience neurological, pulmonary and cardiovascular impairments (Haftel et al. 2024; Nickson 2020).
Complications after AFE may include, but are not limited to:
(Haftel et al. 2024)
The neonatal survival rate is around 70% (Haftel et al. 2024). However, infants who survive may experience cognitive impairment, epilepsy, motor impairment and/or developmental delay due to hypoxic-ischemic encephalopathy (Haftel et al. 2024).
Although AFE cannot be prevented, early diagnosis and intervention may lead to better outcomes for both the birthing parent and the fetus.
As tragic as this condition is, it remains, for the most part, a mystery that can be neither predicted nor prevented.
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