Discover the facts about the little-known killer amniotic fluid embolism

Medicine's best-kept secret is a mysterious disease known as amniotic fluid embolism (AFE). It comes out of nowhere to kill mothers and their babies, usually during childbirth. According to medical literature, as many as half of the women it affects die within an hour of the onset of symptoms and many of the rest die the same day or suffer permanent neurological impairment.

What is AFE?
AFE is a rare obstetric emergency in which amniotic fluid, foetal cells, hair or other debris enters the mother's blood stream via the placenta and triggers an allergic reaction. This allergic reaction then results in cardiorespiratory (heart and lung) collapse.

The condition is so rare that most doctors will never encounter it in their professional careers and as a result the exact process is poorly understood. However, it is believed that once the fluid and foetal cells enter the maternal pulmonary circulation a two-phase process occurs:

First phase: The patient experiences acute shortness of breath and hypertension (extremely high blood pressure). This rapidly progresses to cardiopulmonary arrest as the chambers of the heart fail to dilate and there is a reduction of oxygen to the heart and lungs. Not long after this stage the patient will lapse into a coma.

Second phase: Although many women do not survive beyond the first stage, about 40 per cent of the initial survivors will pass onto the second phase. This is known as the hemorrhagic phase and may be accompanied by severe shivering, coughing, vomiting and the sensation of a bad taste in the mouth. This is also accompanied by excessive bleeding as the blood loses its ability to clot. There is also foetal distress present. As hypoxia (the reduction of the oxygen supply) progresses the foetal heart rate may drop to less than 110 beats per minute (bpm).

What causes AFE?
It is mostly agreed that this condition results from amniotic fluid entering the uterine veins and in order for this to occur there are three prerequisites:

• Ruptured membranes (a term used to define the rupture of the amniotic sac)
• Ruptured uterine or cervical veins
• A pressure gradient from uterus to vein

Although exposure to foetal tissue is common and thus finding foetal tissue within the maternal circulation is not significant, in a small percentage of women this exposure leads to a complex chain of events resulting in collapse and death.

Who does it affect?
AFE affects all races and ethnic groups and although it was previously thought to affect those of advanced age it has since been disproved; as has the original thought that AFE only occurred after a long, hard labour. It can, in fact, occur before, during or after delivery and has also been known to occur during abortion, abdominal trauma and amnioinfusion (an infusion of fluid into the amniotic cavity when there is a lack of amniotic fluid). Statistically, AFE occurs in an estimated 1:8000 - 30,000 pregnancies internationally and in the UK three to four pregnant women a year.

Are there any signs?
Characteristic signs of AFE include larger than average babies being carried past their due date, very hard labour before going into shock, high levels of anxiety, complaints of chills, shortness of breath and vomiting.

What is the survival rate?
Shockingly, maternal mortality is high with figures of around 80 per cent, although the neo-natal survival rate is much better at 70 per cent. Statistics also show that 50 per cent of patients with AFE die within the first hour of the onset of symptoms and a high percentage of women who do survive have permanent neurological impairment.

There is, however, no evidence to indicate that survivors of AFE are at risk for amniotic fluid embolism in future pregnancies and the condition is considered to be unpredictable and unpreventable. The cause is still unknown.

There are, however, plans for a confidential register of all cases of AFE to be established for the UK. The aim is to identify any differences or common factors between survivors and fatalities with the hope that it may help to reduce the number of maternal deaths from this condition.

Helpful charities

Tommy's, The Baby Charity
Tommy's is determined to end the heartache caused by premature birth, miscarriage and stillbirth.

Bliss
Bliss provides information and support for families of babies who are or have been in special care. Phone 0500 618140 for support.

Sands
Sands offers support for parents whose baby dies at or soon after the time of birth. Call the helpline on 020 7436 5881.