Hypertensive States of Pregnancy

Hypertensive states in pregnancy include preeclampsia-eclampsia, chronic hypertension (either essential or secondary to renal disease, endocrine disease, or other causes), chronic hypertension with superimposed preeclampsia, and gestational hypertension (Table 19-1). Preeclampsia is hypertension associated with proteinuria and edema, occurring primarily in nulliparas after the 20th gestational week and most frequently near term. Recent data support the elimination of edema as a diagnostic criterion. Eclampsia is the occurrence of seizures that cannot be attributed to other causes in a preeclamptic patient. Chronic hypertension is defined as hypertension that is present before conception, before 20 weeks' gestation or that persists for more than 6 weeks postpartum. Hypertension is defined as blood pressure equal to or greater than 140/90 mm Hg or an increase in mean arterial pressure of 20 mm Hg. The use of an increase in blood pressure of 30/15 mm Hg over first-trimester values is controversial. Recent data report no increased adverse events in women with these changes. However, an increase in blood pressure by this amount warrants close observation.

Proteinuria is defined as the excretion of 300 mg or more in a 24-hour specimen or 30 mg/dL in a random specimen. Preeclampsia may occur in women with chronic hypertension (superimposed preeclampsia); the prognosis is worse for the mother and fetus than with either condition alone. The criteria for superimposed preeclampsia are worsening hypertension (30 mm Hg systolic or 15 mm Hg diastolic above the average of values before 20 weeks' gestation) together with either nondependent edema or proteinuria.

Gestational hypertension is further divided into transient hypertension of pregnancy if preeclampsia is present at the time of delivery and the blood pressure is normal by 12 weeks postpartum, and chronic hypertension if the elevation in blood pressure persists beyond 12 weeks postpartum. This condition is often predictive of the later development of essential hypertension.

It is frequently difficult to determine whether a patient has preeclampsia, chronic hypertension, or chronic hypertension with superimposed preeclampsia. This is partly because blood pressure normally decreases during the second trimester, and the decrease may mask the presence of chronic hypertension. Renal biopsy studies have shown that only about 70% of primigravidas under 25 years of age with the triad of edema, hypertension, and proteinuria have glomeruloendotheliosis, the characteristic lesion of preeclampsia.

Twenty-five percent have unsuspected renal disease. In multiparas with chronic hypertension with superimposed preeclampsia, about 3% have glomeruloendotheliosis and 21% have underlying renal disease. Renal biopsy is rarely performed in pregnancy because the benefit usually does not justify the risk. The sensitivity and specificity of biochemical markers such as uric acid and antithrombin III are unknown.

BIBLIOGRAPHY
Bosio PM et al: Maternal central hemodynamics in hypertensive disorders of pregnancy. Obstet Gynecol 1999;94:978.

Brockelsby JC et al: The effects of vascular endothelial growth factor on endothelial cells: a potential role in preeclampsia. Am J Obstet Gynecol 2000;182(1Pt 1):176.

Golding J: A randomized trial of low dose aspirin for primiparae in pregnancy. The Jamaica Low Dose Aspirin Study Group. Br J Obstet Gynaecol 1998;105:293.

Herrera JA, Arevalo-Herrera M, Herrera S: Prevention of preeclampsia by linoleic acid and calcium supplementation: a randomized controlled trial. Obstet Gynecol 1998;91:585.

Levine RJ: Should the definition of preeclampsia include a rise in diastolic blood pressure of 15 mm Hg? Am J Obstet Gynecol 2000;182:225.

Levine RJ et al: Trial of calcium to prevent preeclampsia. N Engl J Med 1997;337:69.

Mills JL et al: Prostacyclin and thromboxane changes predating clinical onset of preeclampsia: a multicenter prospective study. JAMA 1999;282:356.

Morriss MC et al: Cerebral blood flow and cranial magnetic resonance imaging in eclampsia and severe preeclampsia. Obstet Gynecol 1997;89:561.

Ranta V et al: Nitric oxide production with preeclampsia. Obstet Gynecol 1999;93:442.

Report of the National High Blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy. Am J Obstet Gynecol 2000;183:S1.

Rotchell YE et al: Barbados Low Dose Aspirin Study in Pregnancy (BLASP): a randomized trial for the prevention of pre-eclampsia and its complications. Br J Obstet Gynaecol 1998;105:286.

Sibai BM: Prevention of preeclampsia: a big disappointment. Am J Obstet Gynecol 1998;179:1275.

Sibai BM et al: Risk factors associated with preeclampsia in healthy nulliparous pregnancy. The Calcium for Preeclampsia Prevention (CPEP) Study Group. Am J Obstet Gynecol 1997;177:1003.

The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med 1997;157:2413.

Taylor RN: Review: immunobiology of preeclampsia. Am J Reprod Immunol 1997;37:79.