CHRONIC HYPERTENSION IN PREGNANCY

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Hypertension is the most common medical disorder during pregnancy. Chronic hypertension is a serious medical complication in pregnancy associated with increased maternal and perinatal morbidity and mortality. Maternal complications include abruptio placentae, stroke, and superimposed preeclampsia. Fetal complications include prematurity, stillbirth, low birth weight, and neonatal death. Careful antepartum, intrapartum, and postpartum management of women with chronic hypertension in pregnancy may reduce morbidity and mortality.

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PREVALENCE

The prevalence of chronic hypertension in pregnancy varies among populations depending on maternal age and ethnicity. Chronic hypertension is observed in 1% to 5% of pregnant women depending on the diagnostic criteria used.62 In recent reports, the incidence was 2.5% among African-Americans and 1% among other racial groups.80 The prevalence of chronic hypertension also varies according to age. The reported rates range from 1.9% at 20 to 29 years to 5.7% at 30 to 39 years among African-Americans

DEFINITION AND DIAGNOSIS

Chronic hypertension is characterized by an elevated blood pressure occurring before pregnancy, by hypertension occurring during pregnancy before 20 weeks' gestation, or by hypertension persisting beyond 6 weeks' postpartum. Hypertension is defined as a systolic blood pressure of at least 140 mm Hg or a diastolic blood pressure of at least 90 mm Hg on at least two occasions at least 4 hours apart.62 In pregnant women whose prepregnancy blood pressure is unknown, the diagnosis of chronic

ETIOLOGY AND CLASSIFICATION

The etiology of essential hypertension remains elusive. Chronic hypertension is a complex disease in which genetic predisposition interacts with multiple environmental factors. The etiology of chronic hypertension is an important consideration in pregnancy. Chronic hypertension can be subdivided into primary (idiopathic) and secondary. Primary idiopathic hypertension accounts for 90% of chronic hypertension seen during pregnancy. Secondary hypertension (10%) is related to several underlying

MATERNAL RISKS

Abruptio placentae in women with chronic hypertension is increased, with a prevalence of up to 10%.91 In women with mild chronic hypertension, the incidence was nearly 1.5% to 2% and was not influenced by antihypertensive treatment.82, 89 The incidence of abruptio placentae in women with severe hypertension ranged from 2.3%84 to 9.5%.82 Sibai and co-workers reported an overall incidence of abruptio placentae of 1.5%. The frequency was significantly higher in women with superimposed preeclampsia

PERINATAL RISKS

The risk of perinatal death is increased two to four times in women with chronic hypertension when compared with the general population.1, 38, 73 In a follow-up study of 337 pregnancies among 298 women with chronic hypertension, the rate of perinatal mortality was 45 in 1000 compared with a rate of 12 in 1000 in the general population (P <0.001).73 Rates for premature deliveries and small-for-gestational age (SGA) infants were also found to be higher in women with chronic hypertension.1, 31, 38

MANAGEMENT

The goal in managing chronic hypertension is to reduce pregnancy-related complications and maternal cerebral hemorrhage. Care for women with chronic hypertension should begin before conception. Drugs that may have adverse side effects on the fetus [e.g., angiotensin-converting enzyme inhibitors (ACE)] should be discussed and discontinued if necessary. Based on the medical history and clinical and laboratory findings, pregnant women with chronic hypertension can be divided into low- or high-risk

LOW-RISK CHRONIC HYPERTENSION

Pregnant women with chronic hypertension are considered to be at low risk in cases of mild hypertension without any organ involvement. The maternal benefits of pharmacologic treatment of mild chronic hypertension are not clear, and whether antihypertensive treatment improves perinatal outcome remains controversial. Few prospective randomized studies have been conducted to determine whether antihypertensive treatments in these women improve maternal or perinatal outcome.4, 14, 30, 34, 35, 44, 68

HIGH-RISK CHRONIC HYPERTENSION

Women with chronic hypertension who are considered high risk have severe hypertension or mild hypertension associated with signs of end-organ involvement, concomitant disease, or a poor obstetric history. This group of patients is at high risk for pregnancy complications, including superimposed preeclampsia, abruptio placentae, SGA infants, and prematurity.55, 73, 84, 88 Patients with renal insufficiency, diabetes (all classes), collagen vascular disease, cardiomyopathy, or coarctation of the

PHARMACOLOGIC TREATMENT

The initiation of pharmacologic treatment of chronic hypertension in pregnant women must take into account the severity of hypertension and the risk of target organ damage. For women with high-risk hypertension, the authors recommend treatment at a diastolic blood pressure of 90 mm Hg or higher. Other clinicians recommend treatment when the diastolic blood pressure is 100 mm Hg or higher in high-risk patients.62 In women with low-risk hypertensive pregnancy, the authors recommend

MEDICATION TO PREVENT SUPERIMPOSED PREECLAMPSIA

Initial reports studying the prophylactic use of low-dose aspirin, ranging from 50 to 150 mg daily, included a limited number of patients.9, 98 Recently, Caritis and co-workers16 studied the effect of low-dose aspirin (60 mg/day) for the prevention of preeclampsia. In this prospective, randomized, double-blind, placebo-controlled trial that included 2539 pregnant women at high risk for the development of preeclampsia, 774 had chronic hypertension. The women were enrolled between gestational

POSTPARTUM MANAGEMENT

Women with high-risk chronic hypertension are at risk for postpartum complications, such as pulmonary edema, hypertensive encephalopathy, or renal failure.91 These risks are particularly increased in women having a target organ involvement, superimposed preeclampsia, abruptio placentae, morbid obesity, or long-standing hypertension. In these women, blood pressure must be closely controlled for at least 48 hours after delivery. Intravenous labetalol or hydralazine can be used as needed51 in

SUMMARY

Pregnant women with chronic hypertension are at risk for maternal and perinatal morbidity. Careful assessment and management of these patients during pregnancy are the keys to reducing maternal and fetal complications. Antihypertensive treatment should be used in women with high-risk chronic hypertension, whereas drug therapy does not improve pregnancy outcome in women at low risk. Prophylactic low-dose aspirin started early in pregnancy in women with chronic hypertension is not effective in

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    Address reprint requests to Jeffrey C. Livingston, MD, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Carilion Roanoke Community Hospital, Prenatal Diagnosis Center, 102 Highland Southeast, Suite 445, Roanoke, VA 24029–2946, e-mail: [email protected]

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