AMNIOTIC FLUID EMBOLISM

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Section 7: Abnormalities of Pregnancy, Labor and Puerperium
AMNIOTIC FLUID EMBOLISM
This condition occurs when amniotic fluid enters the maternal circulation through a tear in the membranes or placenta. The body responds in two phases—The initial phase is one of vasospasm causing hypoxia, hypotension and cardiovascular collapse. The second phase is the development of left ventricular failure, with hemorrhage and coagulation disorder followed by pulmonary edema. Mortality and morbidity are very high.

The presence of thromboplastin rich liquor amnii in the maternal circulation blocks the pulmonary arteries and triggers the complex coagulation mechanism leading to DIC. There will be severe clotting defect with profuse bleeding per vagina or through the venepuncture sites due to consumption of coagulation factors.

Predisposing Factors

Amniotic fluid embolism can occur at any stage in gestation. It is mostly associated with labor, though cases in early pregnancy and postpartum have been reported (Bennett and Brown, 1999).

• Transfer of amniotic fluid from the uterus to the maternal circulation can be insidiously associated with a tear in the membranes
• Amniotic fluid under pressure may enter maternal circulation in the first phase of hypoxia during hypertonic uterine activity
• Procedures such as insertion of an intrauterine catheter and artificial rupture of membranes are associated with the condition
• In cases of placental abruption, the placental bed is disrupted, and the barrier between the maternal circulation and amniotic sac may be breached
• It can occur during a cesarean section or termination of pregnancy or in association with ruptured uterus
• Trauma may occur during intrauterine manipulation such as internal podalic version

The condition is difficult to predict and equally difficult to prevent.

Clinical Features

• Sudden onset of maternal respiratory distress: The woman becomes severely dyspnic and cyanosed
• There is maternal hypotension and uterine hypertonia
• Fetal distress in response to hypoxia caused by hypertonia
• Cardiopulmonary arrest follows quickly in minutes
• Many mothers present with convulsions immediately preceding the collapse (Clark, 1990)

Emergency Management

Any one of the above symptoms is indicative of an acute emergency. The mother may be in a state of collapse and resuscitation must be started at once. Specific management of the condition is life support and high levels of oxygen are required. Mothers who survive may suffer neurological impairment.

Complications

Disseminated intravascular coagulation (DIC) is likely to occur within 30 minutes of the initial collapse.
Acute renal failure occurs due to heavy bleeding and the prolonged hypovolemic hypotension. Transfer to an intensive therapy unit for specialized care is indicated.

Effect on the Fetus

Perinatal mortality and morbidity are high, where amniotic fluid embolism occurs before the birth of the baby. Delay in the time from initial maternal collapse to delivery needs to be minimal if fetal death is to be avoided.

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SHOCK
Shock is defined as a state of circulatory inadequacy with poor tissue perfusion resulting in generalized cellular hypoxia leading to dysfunction of organs and cells.