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How pregnancy incites or aggravates hypertension remains unsolved despite decades of intensive research. Indeed, hypertensive disorders remain among the most significant and intriguing unsolved problems in obstetrics.

Hypertensive disorders complicate 5 to 10 percent of all pregnancies, and together they are one member of the deadly triad—along with hemorrhage and infection—that contributes greatly to maternal morbidity and mortality. Of these disorders, the preeclampsia syndrome, either alone or superimposed on chronic hypertension, is the most dangerous. As subsequently discussed, new-onset hypertension during pregnancy—termed gestational hypertension—is followed by signs and symptoms of preeclampsia almost half the time, and preeclampsia is identified in 3.9 percent of all pregnancies (Martin, 2012).

The World Health Organization (WHO) systematically reviews maternal mortality worldwide, and in developed countries, 16 percent of maternal deaths were reported to be due to hypertensive disorders (Khan, 2006). This proportion is greater than three other leading causes that include hemorrhage—13 percent, abortion—8 percent, and sepsis—2 percent. In the United States from 1998 to 2005, Berg and colleagues (2010) reported that 12.3 percent of 4693 pregnancy-related maternal deaths were caused by preeclampsia or eclampsia. The rate was similar to that of 10 percent for maternal deaths in France from 2003 through 2007 (Saucedo, 2013). Importantly, more than half of these hypertension-related deaths were preventable (Berg, 2005).

Terminology and Diagnosis

In this country for the past two decades, pregnancy hypertension was considered using the terminology and classification promulgated by the Working Group of the National High Blood Pressure Education Program—NHBPEP (2000). To update these, a Task Force was appointed by President James Martin for the American College of Obstetricians and Gynecologists (2013b) to provide evidence-based recommendations for clinical practice. The basic classification was retained, as it describes four types of hypertensive disease:

  1. Gestational hypertension—evidence for the preeclampsia syndrome does not develop and hypertension resolves by 12 weeks postpartum

  2. Preeclampsia and eclampsia syndrome

  3. Chronic hypertension of any etiology

  4. Preeclampsia superimposed on chronic hypertension.

Importantly, this classification differentiates the preeclampsia syndrome from other hypertensive disorders because it is potentially more ominous. This concept aids interpretation of studies that address the etiology, pathogenesis, and clinical management of pregnancy-related hypertensive disorders.

Diagnosis of Hypertensive Disorders

Hypertension is diagnosed empirically when appropriately taken blood pressure exceeds 140 mm Hg systolic or 90 mm Hg diastolic. Korotkoff phase V is used to define diastolic pressure. Previously, incremental increases of 30 mm Hg systolic or 15 mm Hg diastolic from midpregnancy blood pressure values had also been used as diagnostic criteria, even when absolute values were < 140/90 mm Hg. These incremental changes are no longer recommended criteria because evidence shows that such women are not likely to experience increased adverse pregnancy outcomes (Levine, 2000; North, 1999). That said, women who have a ...

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