Amniotic fluid embolism is a rare but serious condition that occurs when amniotic fluid — the fluid that surrounds a baby in the uterus during pregnancy — or fetal material, such as fetal cells, enters the mother's bloodstream. Amniotic fluid embolism is most likely to occur during delivery or in the immediate postpartum period.
Amniotic fluid embolism is difficult to diagnose. If your doctor suspects you might have one, you'll need immediate treatment to prevent potentially life-threatening complications.
Amniotic fluid embolism might develop suddenly and rapidly. Signs and symptoms might include:
- Sudden shortness of breath
- Excess fluid in the lungs (pulmonary edema)
- Sudden low blood pressure
- Sudden failure of the heart to effectively pump blood (cardiovascular collapse)
- Life-threatening problems with blood clotting (disseminated intravascular coagulopathy)
- Bleeding from the uterus, cesarean incision or intravenous (IV) sites
- Altered mental status, such as anxiety or a sense of doom
- Rapid heart rate or disturbances in the rhythm of the heart rate
- Fetal distress, such as a slow heart rate, or other fetal heart rate abnormalities
- Loss of consciousness
Amniotic fluid embolism occurs when amniotic fluid or fetal material enters the mother's bloodstream. A likely cause is a breakdown in the placental barrier, such as from trauma.
When this breakdown happens, the immune system responds by releasing products that cause an inflammatory reaction, which activates abnormal clotting in the mother's lungs and blood vessels. This can result in a serious blood-clotting disorder known as disseminated intravascular coagulation.
However, amniotic fluid embolisms are rare — and it's likely that some amniotic fluid commonly enters the mother's bloodstream during delivery without causing problems. It's not clear why in some mothers this leads to amniotic fluid embolism.
It's estimated that there are between one and 12 cases of amniotic fluid embolism for every 100,000 deliveries. Because amniotic fluid embolisms are rare, it's difficult to identify risk factors.
Research suggests that several factors might be linked to an increased risk of amniotic fluid embolism, however, including:
- Advanced maternal age. If you're 35 or older at the time of your child's birth, you might be at increased risk of amniotic fluid embolism.
- Placenta problems. Abnormalities in the placenta — the structure that develops in your uterus during pregnancy — might increase your risk of amniotic fluid embolism. Abnormalities might include the placenta partially or totally covering the cervix (placenta previa) or the placenta peeling away from the inner wall of the uterus before delivery (placental abruption). These conditions can disrupt the physical barriers between you and your baby.
- Preeclampsia. Having high blood pressure and excess protein in your urine after 20 weeks of pregnancy (preeclampsia) can increase your risk.
- Medically induced labor. Limited research suggests that certain labor induction methods are associated with an increased risk of amniotic fluid embolism. Research on this link, however, is conflicting.
- Operative delivery. Having a C-section, a forceps delivery or a vacuum extraction might increase your risk of amniotic fluid embolism. These procedures can disrupt the physical barriers between you and your baby. It's not clear, however, whether operative deliveries are true risk factors for amniotic fluid embolism because they're used after the condition develops to ensure a rapid delivery.
- Polyhydramnios. Having too much amniotic fluid around your baby may put you at risk of amniotic fluid embolism.
Amniotic fluid embolism can cause serious complications for you and your baby, including:
- Brain injury. Low blood oxygen can cause permanent, severe neurological damage or brain death.
- Lengthy hospital stay. Women who survive an amniotic fluid embolism often require treatment in the intensive care unit and — depending on the extent of their complications — might spend weeks or months in the hospital.
- Maternal death. The number of women who die of amniotic fluid embolism (mortality rate) is very high. The numbers vary, but as many as 20 percent of maternal deaths in developed countries may be due to amniotic fluid embolisms.
- Infant death. Your baby is at risk of brain injury or death. Prompt evaluation and delivery of your baby improves survival.