What are preeclampsia and eclampsia?

Causes and Symptoms

Preeclampsia, also known as toxemia of pregnancy or pregnancy-induced hypertension, is a serious condition that affects 6 to 8 percent of pregnant women, and is a leading cause of premature delivery, maternal death, and perinatal child death. The condition can arise any time from the twentieth week of pregnancy to the first week after birth. A woman is diagnosed with preeclampsia if she has elevated blood pressure in addition to proteinuria. The blood pressure of preeclampsia patients generally exceeds 140/90; however, an increase in systolic pressure by 30 or an increase in diastolic pressure by 15—even if the 140/90 cutoff is not reached—when accompanied by other characteristic symptoms is sufficient for a diagnosis of preeclampsia. Headaches, abdominal pain, and visual disturbances may accompany the disorder. Patients who have normal blood pressure prior to pregnancy but suffer from increased blood pressures as described above are said to suffer from pregnancy-induced hypertension (PIH).

Preeclampsia may lead to HELLP syndrome, characterized by hemolytic anemia, elevated liver enzymes, and a low platelet count. HELLP syndrome typically occurs in the last trimester, with women complaining of nausea, vomiting, and abdominal pain. In severe cases, the syndrome leads to intravascular blood clotting, kidney failure, liver failure, respiratory failure, systemic failure, and death.

Eclampsia, the most dangerous complication of preeclampsia, is characterized by convulsive seizures
that may lead to coma or death. Organ damage, particularly in the kidneys, liver, brain, and placenta, may occur.

The risk of preeclampsia is higher in women experiencing their first pregnancy, or their first pregnancy with a different partner; women with a personal or family history of the disorder; women younger than eighteen or older than forty; those carrying two or more fetuses; women with a body mass index (BMI) greater than 30; women with polycystic ovarian syndrome; or women with other conditions such as diabetes, kidney disease, hypertension, or autoimmune disorders. Recent evidence indicates that the existence of high blood pressure, obesity, or diabetes prior to pregnancy is likely to predispose a pregnant woman to preeclampsia.

The cause of preeclampsia and eclampsia is not usually known. Kidney disease or other conditions that raise blood pressure may trigger the condition. Genetics may be important. An abnormal maternal immune response to fetal tissue may also play a role in triggering preeclampsia and eclampsia. The functioning of the placenta (which develops from the membrane known as the chorion) seems to play an important part in the development of preeclampsia. If it becomes hypoxic (oxygen-deprived), the placenta is believed to release as-yet-unidentified toxic substances into the maternal circulation, leading to the development of preeclampsia.

Treatment and Therapy

If caught early, mild cases of preeclampsia can be treated with strict bed rest, either at home or in the hospital if the condition does not improve. In more severe cases, bed rest should be accompanied by intravenous (IV) administration of balanced salt solution, such as Ringer’s solution; sedatives; medication to control blood pressure; and, if necessary, medication to control seizures, such as magnesium sulfate. Diuretics may also be required. Once the woman’s condition is stabilized, delivery should be accomplished, either vaginally or by cesarean section. Eclampsia and HELLP syndrome should be treated in the same way. If magnesium sulfate fails to control seizures, then drugs such as diazepam should be administered. While delivery of the fetus is often essential for the survival of both the mother and the baby, it frequently results in extremely premature infants who then face a large cadre of challenges associated with their prematurity.

Women treated for preeclampsia and related disorders should be monitored for other symptoms, including headaches, blurred vision, abdominal pain, vaginal bleeding, and loss of fetal heart sounds. Symptoms should resolve themselves within six hours after delivery.

Perspective and Prospects

Although preeclampsia was first described as early as the nineteenth century, little progress has been made since in determining its cause. Recent research has focused on a number of potential factors. Among them are genetics, because of the relationship between a family history of the disorder and the risk of developing it. Some researchers have suggested nutrient deficiencies as a cause, but evidence for a nutritional relationship has been equivocal. Hormonal imbalances have been suggested as a cause, as have interruptions of the blood supply to the placenta, immune system responses to fetal tissue or attempts to repair perceived damage to vascular tissue, calcium deficiencies, and a host of other factors, including preexisting conditions such as lupus, diabetes, sickle cell disease, and kidney diseases.

Researchers seeking the cause of preeclampsia have recently focused on the placenta. Deprivation of vascular growth factors, such as vascular endothelial growth factor
(VEGF), inhibits vascular development in the placenta, which adversely affects the developing fetus. Abnormal concentrations of VEGF have also been shown to cause nephron damage in the kidney.

With growth factors, hormones, nutrients, or myriad other compounds and conditions possibly playing a role in triggering preeclampsia and eclampsia, it is clear that much more work needs to be done.

Bibliography

Barden, Anne. “Pre-eclampsia: Contribution of Maternal Constitutional Factors and the Consequences for Cardiovascular Health.” Clinical and Experimental Pharmacology and Physiology 33, no. 9 (September, 2006): 826–830.

Basso, Olga, et al. “Trends in Fetal and Infant Survival Following Preeclampsia.” Journal of the American Medical Association 296, no. 11 (September 20, 2006): 1357–1362.

Gabbe, Steven G., Jennifer R. Niebyl, and Joe Leigh Simpson, eds. Obstetrics: Normal and Problem Pregnancies. 6th ed. Philadelphia: Elsevier/Saunders, 2012.

Lindheimer, Marshall D., James M. Robert, and F. Gary Cunningham, eds. Chesley’s Hypertensive Disorders in Pregnancy. 3d ed. Amsterdam; Boston: Academic Press/Elsevier, 2009.

National High Blood Pressure Education Program. Working Group Report on High Blood Pressure in Pregnancy. Bethesda, Md.: National Institutes of Health, National Heart, Lung, and Blood Institute, 2000.

NIH. "Preeclampsia and Eclampsia: Condition Information." NIH: Eunice Kennedy Shriver National Institute of Child Health and Human Development, November 30, 2012.

Redman, Chris, and Isabel Walker. Pre-eclampsia—The Facts: The Hidden Threat to Pregnancy. New York: Oxford University Press, 1997.

Savitsky, Diane. "Pre-eclampsia." Health Library, March 14, 2013.