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Hypertension is a common medical disorder that affects 29.1% of adults in the United States and complicates as many as 10% of all pregnancies. Hypertensive disorders of pregnancy rank among the leading causes of maternal morbidity and mortality. There are approximately 50,000–60,000 preeclampsia deaths per year worldwide, and preeclampsia accounted for 9.4% of maternal deaths in the United States between 2006 and 2010. 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 insufficiency, fetal growth restriction, preterm birth, placental abruption, stillbirth, and neonatal death.
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Hypertension is defined as a sustained systolic blood pressure ≥ 140 mm Hg or a sustained diastolic blood pressure ≥ 90 mm Hg or both. In the nonpregnant patient, essential hypertension accounts for > 90% of cases; however, many other conditions must be considered. 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 at or beyond 20 weeks of gestation in patients without evidence of proteinuria. Preeclampsia is characterized by the onset of hypertension and proteinuria or other sequelae, usually during the third trimester of pregnancy, but it can occur at or beyond 20 weeks of gestation. Although the rapid onset of edema was once considered a diagnostic criterion, it has been shown that 10–15% of women with rapid edema remain normotensive. 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 ...