The blood pressure readings are taken on two occasions 6 hours apart, with special attention to the diastolic pressure, which reflects peripheral vascular spasm. A pregnant patient is considered hypertensive when her mean arterial pressure rises 15 mm Hg from her baseline or is over 100 mm Hg. Pathologic changes in the glomeruli of the kidney produce proteinuria, oliguria, and edema. Mild preeclampsia is managed by bed rest to facilitate sodium excretion, which takes place more rapidly when the body is at rest. While resting in bed the patient is positioned on her left side to avoid pressure of the uterus against the vena cava and supine hypotension syndrome.
Rest is often all that is needed to relieve the symptoms of mild preeclampsia.
Some physicians also prescribe a high-protein diet to compensate for the protein lost in the urine and, perhaps, mild restriction of sodium intake. However, restriction of sodium can activate the angiotensin system and cause an undesirable elevation in blood pressure. Diuretics are not used for control of edema because they can only aggravate the condition by increasing glomerular vessel permeability and stimulating angiotension activity. Preeclampsia becomes severe when systolic blood pressure is over 160 mm Hg or the diastolic pressure is over 110 mm Hg. To help establish the diagnosis two blood pressure readings are taken 6 hours apart after the woman has been on bed rest.