|Amniotic Fluid Embolism: A rare
fatal cause of maternal death.
Normal Amniotic fluid:
At a very early period of development amnion (a membrane) covers the fetus.
The amniotic fluid is a clear fluid which fills up the amnion.
The amnion expands and forms the amniotic sac.
The amniotic sac surrounds the fetus.
At term the volume of fluid is 500-1000 ml.
The fluid has a specific gravity of 1007-1025 and contain 98-99 per cent water.
The solids consist of half organic and half inorganic matter.
One litre of amniotic fluid contains about 5gm of protein, 200 mg of glucose and calcium, sodium, potassium and chloride.
Amniotic fluid is formed partly from fetal pulmonary secretion and fetal urine, but mostly by transudation from maternal blood and active transport across the amniotic epithelium.
There is a rapid turnover of the fluid, one third of the volume of water is replaced every hour by water from maternal plasma.
The fluid is removed through drinking by the fetus and by return to the maternal circulation.
The function of the amniotic fluid are to provide the fetus with fluid to drink, to keep the fetus at an even temperature, to cushion it against injury and provide a medium in which it can move easily.
Pathophysiology of Amniotic Fluid Embolism:
Amniotic fluid embolism is a rare fatal complication of pregnancy.
The incidence of this condition is reported to range from 1:8 000 to 1:80 000 pregnancies.
Infusion of amniotic fluid usually occurs during uterine contractions when the head is in the birth canal.
It may also occur following cesarian section.
The amniotic fluid is forced through a rupture in the chorion into the maternal veins, precipitating severe dyspnea, tachypnea and hypotension.
The patient may have hypotensive shock followed by seizure and coma.
Disseminated intravascular coagulation is a common consequence.
At autopsy the lungs are hemorrhagic.
Squamous cells are lodged in the arterioles.
Important pathology finding: Fetal squamous and lanugo hairs noted in pulmonary capillaries as well as in aspirates from the right atrium.
Amniotic debris also contains lipid and mucin, which can be identified by special stains.
Amniotic fluid embolism should be considered as the cause of death when women suddenly dies days or even weeks after delivery due to haemorrhagic shock following post-partum genital bleeding resulting from uterine atony.
"Maternal pulmonary embolism by amniotic fluid as a cause of obstetric shock and unexpected deaths in obstetrics," Journal of the American Medical Association, vol. 117, p. 1245–1254, 1340–1345, 1941.
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