Preeclampsia and Eclampsia Health Article

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.

Causes and symptoms

As previously mentioned, the initial cause of preeclampsia/eclampsia is not known but is thought to be immunologic. The relationship among the three factors that define preeclampsia appears to be as follows. First, the normal increase in blood plasma volume and decrease in peripheral vascular resistance that occur during an uncomplicated pregnancy are absent. The patient's blood vessels allow fluid to leak from the vessels into the surrounding tissue, which results in edema. The seizures that characterize eclampsia result from edema of the brain. The patient's kidneys are under stress because of diminished blood flow through the kidneys and decreased filtration. This process allows protein molecules to spill over into the urine. Damage to the kidneys lowers urine output and increases the levels of sodium in body tissues. Higher concentrations of sodium result in increased fluid retention. Protein lost through the urine also affects the movement of fluid into the tissues, further increasing fluid retention.