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Hypertension is a common medical disorder that affects 20–30% of adults in the United States and complicates as many as 5–8% of all pregnancies. Hypertensive disorders of pregnancy rank among the leading causes of maternal morbidity and mortality. Approximately 15% of maternal deaths are attributable to hypertension, making it the second leading cause of maternal mortality in the United States. Severe hypertension increases the mother's risk of heart attack, cardiac failure, cerebral vascular accidents, and renal failure. The fetus and neonate also are at increased risk from complications such as poor placental transfer of oxygen, fetal growth restriction, preterm birth, placental abruption, stillbirth, and neonatal death.
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Hypertension is defined as a sustained blood pressure higher than 140/90 mm Hg. In the nonpregnant patient, essential hypertension accounts for more than 90% of cases; however, many other conditions must be considered (Table 26–1). In the pregnant patient, hypertension may be attributable to any of the conditions summarized in Table 26–1. In addition, unique forms of hypertension, gestational hypertension and preeclampsia, occur only during pregnancy. Gestational hypertension is characterized by elevated blood pressure diagnosed for the first time during pregnancy in patients without evidence of proteinuria. Preeclampsia is characterized by the onset of hypertension and proteinuria, usually during the third trimester of pregnancy. The National High Blood Pressure Education Program Working Group stated that edema occurs too frequently in normal pregnant women to be a useful marker in the diagnosis of preeclampsia. Therefore, edema is no longer recommended as a diagnostic criterion for preeclampsia. Management of preeclampsia differs from the management of other forms of hypertension during pregnancy. Therefore, it is important to distinguish preeclampsia from other forms of hypertension that may complicate pregnancy.
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Classification of hypertension during pregnancy can be viewed as a continuum. On one end of the spectrum is the patient with hypertension that was present before pregnancy (or was recognized during the first half of pregnancy), does not worsen appreciably during pregnancy, and persists after delivery. This condition would be classified as chronic hypertension. On the other end of the spectrum is the patient with no evidence of chronic hypertension who experiences the abrupt onset of hypertension and proteinuria late in pregnancy followed by complete resolution postpartum. In this case, the hypertension observed during pregnancy may be the result of factors related entirely to pregnancy and not to an underlying medical cause. This condition would be classified as preeclampsia. Between these 2 extremes are gestational hypertension and cases in which varying degrees of preeclampsia ...