Causes of Eclampsia

Eclampsia is a life-threatening condition involving seizures and may occur in some women who develop preeclampsia during pregnancy.

What Causes Preeclampsia and Eclampsia?

The causes of preeclampsia and eclampsia remain unknown, but there are theories. Growing evidence suggests that women with preeclampsia have abnormal placentas that cause damage to the mother's vascular endothelial tissue (the tissue that lines blood vessels). Endothelial cell dysfunction may trigger the symptoms that develop in preeclampsia.

Presumably, as blood pressure rises due to preeclampsia, the blood vessels in the brain increase their resistance, sometimes in spasms. As you develop eclampsia and seizures, your resistance drops, and your brain's system for regulating blood pressure shifts out of balance. This can cause extra-high blood pressure in the brain, edema (swelling) and hemorrhage (bleeding).

Endothelial Damage and Hypertension

Current research suggests that preeclampsia arises from poor oxygen flow to the placenta due to problems with the development of the placenta. As a result, the diseased placenta then releases factors such as sFlt1 (a protein that causes damage to endothelial and placental cells). Damage to endothelial cells eventually lead to the signs and symptoms of preeclampsia including hypertension, proteinuria, and liver dysfunction. Scientists have recently discovered that sFlt1 interferes with the growth and development of endothelial and placental cells. Animal research, involving the injection of sFlt1 into pregnant rats, has shown such measures to develop preeclampsia.

Many women with preeclampsia have higher levels of sFlt1 circulating in their blood than women with normal pregnancies. Although all women with preeclampsia do not have higher levels of sFlt1, it is proposed that other undiscovered factors released from the placenta play a role in the development of preeclampsia.

Edema

Elevated pressure in blood vessels and damaged endothelial tissue causes the fluid in the blood vessels to flow to surrounding tissue. This can cause edema (swelling) in the brain, retinas, lungs, liver, and subcutaneous tissues. Edema is one of the central features of preeclampsia.

Proteinuria

Hypertension and endothelial damage to capillaries (small blood vessels) in the kidneys cause a breakdown in the kidney's functions. This results in proteins-which are generally retained by the body-being excreted in the urine ( proteinuria ), a symptom of preeclampsia.

Women with mild preeclampsia are unlikely to have any symptoms other than mildly elevated blood pressure, proteinuria, and edema. These symptoms usually disappear soon after delivery. Severe preeclampsia can affect various organ systems in the mother and put both mother and her baby at risk for complications.

What Complications May Develop?

The risk of complications depends on the severity of the condition and how early in pregnancy it develops. Though mild preeclampsia typically only causes temporary high blood pressure, proteinuria and edema, it can quickly evolve to severe preeclampsia : more severely elevated blood pressure and proteinuria (protein in the urine), headaches, abdominal pain, visual disturbances, and other symptoms. Although serious complications are rare, damage to endothelial tissue, blood pressure problems, edema, and proteinuria can lead to complications, such as:

• low levels of red blood cells ( anemia ) and low blood platelet levels (thrombocytopenia, which leads to impaired blood clotting) can cause problems during and after labor;
• cerebral edema (swelling of the brain), vasoconstriction (narrowing of the vessels), and damage to capillary (small blood vessel) linings may lead to seizures ( eclampsia ) or hemorrhage ( stroke );
• edema affecting the retinas of the eyes may lead to visual disturbances, retinal detachment, or blindness;
• fluid loss across damaged capillary endothelium in the lungs may result in pulmonary edema (fluid accumulation in the lungs, a potentially life-threatening complication);
• edema of the liver and/or loss of blood supply due to the constriction of blood vessels ( ischemia ) may cause liver cell damage and elevated liver enzymes. Pain in the epigastrium (the right upper quadrant of the abdomen) is attributed to stretching of Glisson's capsule (the fibrous connective tissue surrounding blood vessels of the liver) by swelling or bleeding; or
• kidney failure and heart attack.

One out of every 1,000 women with mild preeclampsia and one out of every 50 women with severe preeclampsia develops eclampsia (seizures). Preeclampsia can also lead to another serious complication, the HELLP syndrome. HELLP is characterized by a blood clotting disorder, hemolytic anemia from the rapid destruction of red blood cells, and liver dysfunction.

Eclampsia and the HELLP syndrome are medical emergencies that usually require immediate delivery of the baby and continued treatment after giving birth. In some women, eclampsia can occur within 4 weeks after delivery. Almost 2% of women in developed countries who have eclamptic seizures die.

How Can Preeclampsia Affect the Baby?

The effect of preeclampsia on the placenta (through which the baby is nourished) may include a reduction in blood flow, nutrients, and oxygen to the fetus. The effects can be significant if severe preeclampsia develops before delivery-the baby may suffer reduced oxygenation, leading to premature delivery and small size. Prematurity and low birth weight are the leading causes of complications and death in babies born to mothers with severe preeclampsia. Depending on the age of the fetus, eclampsia causes fetal death in nine to 23% of cases.