Amniotic fluid embolism (AFE)

Amniotic fluid embolism (AFE) is a serious but rare medical condition affecting pregnant women, usually during or immediately after labor and delivery. AFE is also called anaphylactoid syndrome of pregnancy and occurs when amniotic fluid or fetal material (such as fetal cells) enters the mother’s bloodstream. AFE may be life-threatening but only occurs in about two to eight in one hundred thousand pregnancies. Determining an exact frequency is difficult because nonfatal occurrences of the condition often go unreported. AFE is a serious childbirth complication, and is the second-leading cause of peripartum maternal death and the leading cause of peripartum cardiac arrest in the United States.

Background

Doctors first noticed the passage of amniotic fluid from the uterus into the maternal circulatory system in 1926 and noted AFE occurring during childbirth in 1941. Because the condition is so rare, however, physicians still do not understand its exact pathophysiology. The condition was so named because early researchers thought it was similar to an embolism. However, continued research has indicated that AFE is closer to anaphylaxis than an embolism. Doctors believe that the introduction of amniotic fluid—the fluid surrounding the fetus in the uterus—or fetal material into the mother’s bloodstream causes an anaphylaxis-like, inflammatory reaction inside the mother’s body. However, doctors believe that amniotic fluid or fetal materials may pass into the mother’s bloodstream without causing AFE and do not yet know why some patients have the extreme response and others do not.

Overview

AFE typically occurs during or soon after labor and can occur during vaginal or caesarean delivery. It can also occur during the second trimester during dilation and evacuation procedures. Doctors believe that AFE occurs because of a breakdown in the placental barrier that allows the amniotic fluid or fetal material to pass into the maternal bloodstream. Risk factors for AFE are also difficult to identify because the complication is so rare. However, some of the most likely include advanced maternal age (35 years old or older), placenta abnormalities (including placenta previa and placenta abruption), medically induced labor, polyhydramnios (having too much amniotic fluid around the fetus), and preeclampsia (a condition marked by high blood pressure and protein in the urine), and a pregnancy with multiple fetuses.

The onset of AFE symptoms is usually abrupt, and the health of the mother and the fetus can decline rapidly. The first signs of AFE are often chest pain, shortness of breath, and nausea. The immune response in the patient’s body causes abnormal clotting, specifically in the lungs and blood vessels. Patients can develop disseminated intravascular coagulation (DIS), a serious blood-clotting disorder that occurs because of bleeding from the uterus or intravenous (IV) site. AFE can also cause shortness of breath and an altered mental status such as developing a sense of impending doom. Patients nearly always go into cardiac arrest and acute hypotension is a symptom. They may experience chills, but their body temperature generally does not change. They might also experience pulmonary edema, which is excess fluid in the lungs. The mother often has a rapid heart rate and abnormal breathing. She might have a blue discoloration of the mucous membranes because of a lack of oxygen moving through her body, which can be exacerbated by a sudden narrowing of the blood vessels. After this, the mother often has seizures or a loss of consciousness.

Fetal distress, such as having a slow heart rate, is also common. When doctors detect fetal distress, they often want to deliver the baby as quickly as possible to help protect both the fetus and mother.

Doctors generally diagnose AFE by ruling out other complications. They also conduct a number of tests to diagnose AFE. They will run blood tests to examine the patient’s clotting ability, heart enzymes, electrolytes, and complete blood counts. They may also conduct an electrocardiogram and an echocardiogram and take X-rays to examine the fluid around the heart.

Once doctors have made a diagnosis of AFE, they will quickly and excessively begin treatment. AFE has no definitive cure, so doctors follow basic protocols to treat the effects of the condition. The treatments they use depend on the situation but they often focus on normalizing oxygen levels and the heart rate. Often one of the first treatments is the administration of oxygen to keep blood saturation at normal levels. Doctors will intubate patients who do not achieve normal saturation rates through supplemental oxygen. Patients who are unconscious may receive cardiopulmonary resuscitation (CPR). Another common treatment is catheter placement. Doctors place arterial catheters to monitor blood pressure and venous catheters to give blood transfusions, give medications, and draw blood. Blood transfusions are also extremely common. Because increased blood loss is common, many patients will need numerous transfusions of whole blood, blood products, and replacement fluids.

AFE is a serious medical problem for both the mother and fetus. A mother may experience brain injury because of severe hypoxia (a condition in which the body is deprived of sufficient oxygen). Some women experience a loss of consciousness. Maternal mortality is another possible outcome of AFE, which is the second-leading cause of maternal mortality in the United States. Between 8 and 10 percent of patients with AFE die. Some experience brain death. Quick treatment and quick delivery of the fetus help increase the chances of the mother surviving. AFE can also cause numerous complications for infants after they are born. Brain injury is a concern for infants, as they can also suffer from oxygen loss due to the mothers’ hypoxia. Infants may also die because of hypoxia, a low heart rate, and other complications. Infants who are examined and treated promptly after delivery have higher rates of survival.

Bibliography

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