Amniotic Fluid Embolism

Entry of amniotic fluid into the maternal circulation was first described in 1926 by JR Meyer, however, the first recorded maternal death from amniotic fluid embolism was not until 1941.¹

Incidence

Rare in UK, occurring in only 3.7 per million pregnancies but the fifth commonest cause of perinatal mortality. The incidence has steadily declined over the last 40 years.²

Significant premonitory signs and symptoms i.e.

• Respiratory distress
• Cyanosis
• Restlessness
• Altered behaviour

These may give the first clue to diagnosis before collapse and haemorrhage occur.
The classical scenario of amniotic fluid embolism involves an older multiparous woman in advanced labour who suddenly collapses.
It can occur following

• Termination of pregnancy
• Amniocentesis
• Placental abruption
• Trauma
• During caesarean section and
• Unexpectedly up to 30 minutes after delivery

There may be cardiotocographic abnormalities, uterine hypertonus and an obstetric intervention such as artificial rupture of the membranes.³
Initial pulmonary symptoms may be minor. Amniotic fluid embolises to the pulmonary circulation, and the patient responds with collapse, shock, tachycardia, cardiac irregularity and arrest, and sometimes death.

High index of suspicion on clinical criteria, as above.
Post-mortem will reveal fetal squamous cells and hair (lanugo) in the maternal pulmonary circulation.

Women with symptoms suspicious of amniotic fluid embolism should be transferred to intensive care as soon as possible, as these women may have a better chance of survival.²Treatment is supportive.

Non-Drug

• Resuscitation with oxygen to maintain normal Oxygen saturation. Intubate if necessary.
• Fluids to maintain BP
• Consider pulmonary artery catheterization in patients who are haemodynamically unstable.
• Initiate cardiopulmonary resuscitation (CPR) if the patient arrests. If she does not respond to resuscitation, perform a perimortem caesarean delivery.
• Continuously monitor the fetus.

Drugs

• Dopamine if pulmonary artery catheter can be inserted (coagulopathy may prevent this).
• Otherwise, rapid digitalisation needs to be considered.
• Management of coagulopathy.⁴ Treat coagulopathy with:
  • FFP for a prolonged APTT
  • Cryoprecipitate for a fibrinogen level less than 100 mg/dL
  • Transfuse platelets for platelet counts less than 20,000/mL

Surgical

Umbilical artery embolisation has been described in 2 cases, with excellent survival.⁵

The United Kingdom Amniotic Fluid Embolism Register⁶ was established to identify the incidence of the condition and examine any differences or common factors between survivors and fatalities. There is mandatory reporting of cases. In reported cases from1997-2004 the mortality is 37%. Of those that die, a quarter are dead within the first hour and most of the remainder by nine hours after presentation.

Causes a high level of morbidity for mother and baby.If the patient survives disseminated intravascular coagulation is a common complication.In the 31 survivors between 1997-2004.

• 12 women had a cardiac arrest
• 7 had a hysterectomy
• 2 had further laparotomies
• 1 had subglottic stenosis
• 2 had persisting neurological impairment
• 24 of the 31 survivors were admitted to intensive care units

The majority of women will survive. Hypoxic ischaemic encephalopathy and cerebral palsy are found amongst surviving neonates.