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An eclamptic convulsion sometimes occurs without warning, “like a bolt from a clear sky”, in women who are apparently in perfect health. In the majority of cases, however, the outbreak is preceded for a longer or shorter period by premonitory symptoms indicative of toxemia of pregnancy, among the more common being oedema, headache, epigastric pain, and possibly disturbances of vision.
—J. Whitridge Williams (1903)
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At the time of this textbook’s first edition, it was accepted that “toxemia” preceded most cases of eclampsia. The central role of hypertension had not yet been discovered, and after many years, it became apparent that preeclampsia was a syndrome of which hypertension was only one important facet. Still, the mechanisms by which pregnancy incites or aggravates hypertension remain unsolved. Indeed, hypertensive disorders remain among the most significant and intriguing unsolved problems in obstetrics. These disorders complicate 5 to 10 percent of all pregnancies, and together they are one of the deadly triad—along with hemorrhage and infection—that contributes greatly to maternal morbidity and mortality rates. Of hypertensive 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 4 to 5 percent of all pregnancies (Martin, 2012).
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The World Health Organization (WHO) systematically reviews maternal mortality worldwide, and in developed countries, 16 percent of maternal deaths were attributed to hypertensive disorders (Khan, 2006). In the United States from 2011 to 2013, 7.4 percent of 2009 pregnancy-related maternal deaths were caused by preeclampsia or eclampsia (Creanga, 2017). A similar rate was 10 percent in France from 2003 through 2007 (Saucedo, 2013). Importantly, more than half of these hypertension-related deaths were deemed preventable (Berg, 2005).
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TERMINOLOGY AND DIAGNOSIS
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To update and codify the terminology and classification of hypertensive disorders of pregnancy, a Task Force of the American College of Obstetricians and Gynecologists (2013) has provided evidence-based recommendations for clinical practice. The previous basic classification was retained and describes four types of hypertensive disease:
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Preeclampsia and eclampsia syndrome
Chronic hypertension of any etiology
Preeclampsia superimposed on chronic hypertension
Gestational hypertension—definitive evidence for the preeclampsia syndrome does not develop and hypertension resolves by 12 weeks postpartum.
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Importantly, this classification differentiates the preeclampsia syndrome from other hypertensive disorders because it is potentially more ominous.
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Diagnosis of Hypertensive Disorders
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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 above blood pressure values taken at midpregnancy had also been used as diagnostic criteria, even ...