Clinical Review

Hypertension in pregnancy: Tailoring treatment to risk

OBG Manag. 2003 July;15(7):58-68

Not all hypertensive gravidas should receive drug therapy. In fact, antihypertensive medications should be halted in some patients. Here, 2 experts present a comprehensive plan for high- and low-risk women.

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References

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3. Hermida RC, Ayala DA, Mojon A, et al. Blood pressure patterns in normal pregnancy, gestational hypertension, and preeclampsia. Hypertension. 2000;36:149-158.

4. Sibai BM, Abdella TN, Anderson GD. Pregnancy outcome in 211 patients with mild chronic hypertension. Obstet Gynecol. 1983;61:571-576.

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6. Sibai BM, Mabie WC, Shamsa F, Villar MA, Anderson GD. A comparison of no medication versus methyldopa or labetalol in chronic hypertension during pregnancy. Am J Obstet Gynecol. 1990;162:960-966.

7. Sibai BM. Diagnosis and management of chronic hypertension in pregnancy. Obstet Gynecol. 1991;78:451-461.

8. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin #29: Chronic hypertension in pregnancy. Washington, DC: ACOG; 2001.

9. Sibai BM. Chronic hypertension in pregnancy. Obstet Gynecol. 2002;100:369-377.

10. Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. The sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Arch Intern Med. 1997;157:2413-2446.

11. Ferrer RL, Sibai BM, Murlow CD, Chiquette E, Stevens KR, Cornell J. Management of mild chronic hypertension during pregnancy: a review. Obstet Gynecol. 2000;96:849-860.

12. Umans JG, Lindheimer MD. Antihypertensive treatment. In: Lindheimer MD, Roberts JM, Cunningham FG, eds. Chesley’s Hypertensive Disorders in Pregnancy. 2nd ed. Norwalk, Conn: Appleton and Lange; 1998;581-604.

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KEY POINTS

The treatment goal is to reduce blood pressure to a safe level to prevent maternal cerebral complications.This goal must be weighed against the risks of fetal exposure to antihypertensive drugs and the effects on uteroplacental blood flow.
Gravidas with uncomplicated mild hypertension are at low risk; however, those with severe hypertension or associated complicating factors are at high risk of complications and adverse outcomes.
Antihypertensive medications should not be used routinely in low-risk patients.
Women with high-risk chronic hypertension are at risk for postpartum complications such as pulmonary edema, hypertensive encephalopathy, and renal failure.

The decision to use antihypertensive drug therapy in pregnant women is a tricky one—especially considering the ever-evolving nature of treatment. For instance, we now know that in some hypertensive gravidas, medical interventions may actually be deleterious.

With the aging of the obstetric population in the United States, hypertension in pregnancy—which currently affects 7% of gestations—will remain a major issue in preconception and prenatal care. Its reported risks, which include stroke, pulmonary edema, and death, underscore the importance of careful management (TABLE 1).

This article describes the indications for antihypertensive therapy in pregnancy, focusing on 2 basic categories—high-risk and lowrisk patients—and offers guidance in choosing the optimal agent for each patient.

TABLE 1

Maternal risks of severe hypertension in pregnancy

Stroke
Cerebral hemorrhage
Hypertensive encephalopathy
Congestive heart failure/pulmonary edema
Acute renal dysfunction/acute renal failure
Abruptio placentae
Disseminated intravascular coagulopathy
Death

Correct classification helps direct management

First, identify chronic hypertension. Chronic hypertension is defined as an elevation in blood pressure (BP) that exists prior to pregnancy. Unfortunately, because the pregestational BP is not always known, the diagnosis in many cases must be made on the basis of specific levels: systolic BP of at least 140 mm Hg or diastolic BP of at least 90 mm Hg on at least 2 occasions at least 4 hours apart prior to 20 weeks’ gestation.¹

Even with these guidelines, however, diagnosis may be difficult, since early manifestations of preeclampsia can include hypertension prior to 20 weeks’ gestation.^2,3 In addition, the physiologic decrease in BP during the first and second trimesters—seen in many patients with chronic hypertension—may obscure the condition early in gestation and lead to the erroneous diagnosis of gestational hypertension or preeclampsia later in pregnancy.^4-6

Once a diagnosis of chronic hypertension is made, an accurate classification of the disease will help guide management and initiation of antihypertensive medication.

Mild versus severe hypertension. In pregnancy, chronic hypertension is classified as mild or severe. Mild hypertension has traditionally been defined as systolic BP less than 160 mm Hg and diastolic blood pressure less than 110 mm Hg.^1,7 However, the American College of Obstetricians and Gynecologists recently changed its definition of mild hypertension to systolic BP less than 180 mm Hg.^8,9 Most women with chronic hypertension in pregnancy have the mild form of the disease.

Low-risk hypertension. Patients with uncomplicated chronic mild hypertension are at low risk.

High-risk hypertension. Patients at high risk have either chronic severe hypertension or chronic mild hypertension in association with any of the complicating factors listed in TABLE 2.

History and laboratory studies. To properly classify the disease when first evaluating a patient with chronic hypertension, a thorough history is essential. Ask about related medical illnesses as well as target organ damage. Pay special attention to cardiac, renal, thyroid, and cerebrovascular disease, as well as diabetes. The outcomes of prior pregnancies also are important, especially complications such as abruptio placentae, preeclampsia, preterm delivery, growth restriction, fetal death, and neonatal complications.

Overall, regardless of the treatment, perinatal mortality is not improved with antihypertensive medications for mild hypertension.

Finally, laboratory evaluation should include urine analysis, urine culture, 24-hour urine protein, electrolytes, complete blood count, and glucose tolerance testing.

Other key examinations. In women with long-standing disease, ophthalmologic evaluation, electrocardiography, echocardiography, and assessment of creatinine clearance may be indicated.

TABLE 2

Criteria for low- versus high-risk chronic hypertension

LOW-RISK CHRONIC HYPERTENSION
Chronic mild hypertension (systolic blood pressure 140–160 mm Hg and diastolic blood pressure 90–110 mm Hg) in the absence of complicating factors
HIGH-RISK CHRONIC HYPERTENSION
Either:
Chronic severe hypertension (systolic blood pressure ≥180 mm Hg and diastolic blood pressure ≥110 mm Hg)
or
Chronic mild hypertension (systolic blood pressure 140–160 mm Hg and diastolic blood pressure 90–110 mm Hg) in association with anyof the following: Hypertension for >4 years Maternal age >40 years Renal disease Cardiomyopathy Coarctation of the aorta Retinopathy Diabetes (classes B to F) Collagen vascular disease Antiphospholipid antibody syndrome with perinatal loss Previous severe preeclampsia with perinatal death

Objective of treatment: Prevent complications

In the nonpregnant state, the aim of hypertensive management is to prevent longterm vascular complications such as stroke and cardiovascular disease.¹⁰ A reasonable treatment goal for patients with mild to moderate hypertension may be benefits that are apparent after 5 years of therapy¹⁰—an acceptable time frame due to the long-term nature of the disease.