What causes amniotic fluid embolism?

Amniotic fluid embolism is a condition that many women will experience during the delivery process, which seriously threatens the life safety of the mother and fetus. So what exactly causes amniotic fluid embolism? Many people are not very clear about this. In fact, there are three causes of amniotic fluid embolism. The first cause is excessive pressure in the amniotic cavity membrane.

1. The pressure in the amniotic cavity membrane is too high

After delivery, especially during the second stage of labor, the pressure in the amniotic cavity increases (up to 100-175 mmHg) and significantly exceeds the venous pressure. Therefore, the amniotic fluid may be squeezed into the damaged microvessels and enter the maternal blood circulation.

2. Opening of blood sinuses

Cervical lacerations caused by various reasons during delivery can allow amniotic fluid to enter the maternal blood circulation through damaged blood vessels. When placenta previa, placental abruption, or rupture of the placental marginal sinus occurs, amniotic fluid can also enter the maternal blood circulation through damaged blood vessels or retroplacental sinusoids. During cesarean section or curettage, amniotic fluid can also enter the maternal blood circulation through the blood sinuses at the placenta attachment site, causing amniotic fluid embolism.

3. Rupture of membranes

Most amniotic fluid embolisms occur after rupture of the fetal membranes, and amniotic fluid can enter the maternal blood circulation through damaged small blood vessels in the uterine decidua or cervical canal. During a caesarean section, amniotic fluid can enter the mother's blood circulation through the surgical incision.

In summary, advanced primiparas, multiparas, excessive uterine contractions, premature labor, premature rupture of membranes, placenta previa, uterine rupture, and cesarean section are the predisposing factors of amniotic fluid embolism.