Catastrophic complications of pregnancy in which amniotic fluid, fetal cells, hair, or other debris enters into the maternal pulmonary circulation, causing cardiovascular collapse.
History:
Amniotic fluid embolism was first reported by Ricardo Meyer in 1926. It was reported again in an experiment on laboratory animals by Warden in 1927. The importance of this condition and these early studies was not established until 1941, when Steiner and Lushbaugh reported the clinical and pathological findings of 42 women who died suddenly during or just after labor. The histopathology of the pulmonary vasculature of these women included mucin, amorphous eosinophilic material, and squamous cells. These findings formed the “classic” pathologic findings in AFE.
Etiology
Risk factors:
United Kingdom Obstetric Surveillance System [UKOSS] report
- Induction of labor
- Cesarean section
- Placenta previa and placental abruption (3-10x greater risk)
- Eclampsia
- Multiple pregnancies
- Maternal age ≥35 years
Pathophysiology
Multifactorial pathogenesis:
- Mechanical obstruction of vessels caused by AFE
- Subsequent inflammatory effect by AFE on maternal circulatory system
- Additional immunological mechanisms
Clinical features
Amniotic fluid embolism typically occurs during labor and delivery or in the immediate postpartum period, after caesarean delivery, amniocentesis, removal of placenta, or with therapeutic abortion.
Classical triad:
All of these must occur during labor, cesarean delivery, dilation and evacuation, or within 30 min postpartum with no other explanation of findings.
- Hypoxia
- Hypotension
- Consumptive coagulopathy (including prolongation of coagulation times, hypofibrinogenemia and fibrinolytic activation, etc) and thrombocytopenia
Diagnosis
AFE remains a diagnosis of exclusion, dependent on bedside evaluation and judgment.
American Society for Maternal-Fetal Medicine criteria:
- Sudden cardiopulmonary collapse, or hypotension (systolic blood pressure <90 mmHg) with hypoxia (SpO2<90%)
- DIC, according to ISTH definition
- Symptomatology either during labor or during placental delivery (or up to 30 minutes later)
- No fever
Differential diagnosis:
Management
The management of AFE is supportive and directed towards the maintenance of oxygenation, cardiac output and blood pressure, and correction of the coagulopathy. Treatment should take place in an intensive care unit, if possible.
