Preeclampsia and Eclampsia Health Article

Definition

Preeclampsia and eclampsia are hypertensive disorders of pregnancy that occur in 5%–10% of pregnancies. In developing countries, hypertensive disorders of pregnancy are the single most common cause of death in childbirth. Preeclampsia is defined by the presence of three elements: hypertension, proteinuria (protein in the urine), and edema (fluid retention). If seizures develop following the appearance of the first three factors, the condition is called eclampsia.

Description

The cause of preeclampsia is unknown, but is thought to be an immunologic disorder of some kind. Preeclampsia is more likely to develop in primigravidas (women in their first pregnancy); in women who have used barrier methods of contraception; in women who have new sexual partners; and in women whose birth parents have similar HLA antigens. Other risk factors include a family history of preeclampsia; age extremes in the mother (younger than 20 years or older than 40); preexisting kidney disease or vascular disorder; diabetes; multiple pregnancy; five or more previous pregnancies; African American descent; and genetic abnormalities in the fetus. Since the 1980s, preeclampsia has been associated with poor blood supply to the placenta or placental dysfunction, but the stages in the development of the disorder between damage to the placenta and the appearance of hypertension are not yet fully understood.

Hypertensive disorders of pregnancy affect six major systems or sites in the body: the central nervous system (CNS); kidneys; liver; the blood; the blood vessels; and the fetus and placenta. In severe cases, the mother may suffer liver failure, rupture of the liver, or pulmonary edema (fluid in the lungs); the fetus may die.

Classification of hypertensive disorders of pregnancy

The most common classification used to define hypertensive disorders of pregnancy is the one recommended by the American College of Obstetricians and Gynecologists (ACOG) and endorsed by the NIH Working Group on High Blood Pressure:

• Chronic hypertension, defined as blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic present prior to pregnancy or before the 20th week of pregnancy. During pregnancy the hypertension remains, but proteinuria does not occur. Women who develop hypertension during pregnancy, without proteinuria or seizures, and whose blood pressure remains elevated after pregnancy are also diagnosed with chronic hypertension.
• Gestational hypertension, defined as elevated blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic that arises after midpregnancy with no proteinuria. Blood pressure returns to normal by 12 weeks postpartum. Final diagnosis of this condition is delayed until the postpartum period. If the patient does not develop preeclampsia, and her blood pressure returns to normal, the final diagnosis is transient hypertension of pregnancy. If her blood pressure remains elevated, a diagnosis of chronic hypertension is given.
• Preeclampsia and eclampsia. Preeclampsia is characterized by blood pressure greater than or equal to 140 mm Hg systolic or 90 mm Hg diastolic occurring after midpregnancy (20 weeks gestation), and accompanied by proteinuria. Preeclampsia may be further categorized as mild or severe. A woman is considered to have severe preeclampsia when her blood pressure reading is 160+ mm Hg systolic or 110+ mm Hg diastolic; her proteinuria is equal to or greater than 5 mg of protein in the urine per 24 hours; or other organ systems are involved. She may have headache, visual disturbances, or other CNS symptoms; pulmonary edema, cyanosis, or other cardiovascular symptoms; and abdominal pain.
• Preeclampsia superimposed on chronic hypertension. Pregnant women with preexisting chronic hypertension may develop preeclampsia. Superimposed preeclampsia is suspected when proteinuria develops or increases suddenly; when previously controlled hypertension exhibits a sudden increase; or when the patient develops thrombocytopenia or elevated liver enzyme levels. Women with preeclampsia superimposed on chronic hypertension have a poorer prognosis than women with either condition alone.

Measurement of blood pressure

For purposes of accuracy and standardization, health professionals should take blood pressure measurements in pregnant women with the patient seated rather than lying on her side, because substantial differences exist between the blood pressures in the upper and lower arms when the patient is lying on her side. In addition, the National Institutes of Health (NIH) recommends that the diastolic pressure reading should be taken at Korotkoff 5, with the disappearance of sound—not at Korotkoff 4, when sound becomes muffled. To meet strict criteria for hypertension, the patient's readings must be elevated on at least two separate occasions at least six hours apart.