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4

(See also Hypertension.)

Hypertension (BP ≥ 140/90 mm Hg) during pregnancy can be classified as one of the following:

• Chronic: BP is high before pregnancy or before 20 wk gestation. Chronic hypertension complicates about 1 to 5% of all pregnancies.
• Gestational: Hypertension develops after 20 wk gestation (typically after 37 wk) and remits by 6 wk postpartum; it occurs in about 5 to 10% of pregnancies, more commonly in multifetal pregnancy.

Both types of hypertension increase risk of preeclampsia, eclampsia (see Abnormalities of Pregnancy: Preeclampsia and Eclampsia), and other causes of maternal mortality or morbidity, including hypertensive encephalopathy, stroke, renal failure, left ventricular failure, and the HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count). Risk of fetal mortality or morbidity increases because of decreased uteroplacental blood flow, which can cause vasospasm, growth restriction, hypoxia, and abruptio placentae. Outcomes are worse if hypertension is severe (BP > 180/100 mm Hg) or accompanied by renal insufficiency (eg, creatinine clearance < 60 mL/min, serum creatinine > 2 mg/dL [> 180 μmol/L]).

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Diagnosis

BP is measured routinely at prenatal visits. If severe hypertension occurs for the first time in pregnant women who do not have a multifetal pregnancy or gestational trophoblastic disease, tests to rule out renal artery stenosis, coarctation of the aorta, Cushing's syndrome, SLE, and pheochromocytoma should be considered (see Hypertension: Testing).

Treatment

• For mild hypertension, conservative measures followed by antihypertensives if needed
• MethyldopaSome Trade Names
  ALDOMET
  Click for Drug Monograph
  , β-blockers, or Ca channel blockers tried first
• Avoidance of ACE inhibitors, aldosterone antagonists, and thiazides
• For moderate or severe hypertension, antihypertensive therapy, close monitoring, and, if condition worsens, possibly termination of pregnancy or delivery, depending on gestational age

Treatment of mild to moderate hypertension without renal insufficiency during pregnancy is controversial; the issues are whether treatment improves outcome and whether the risks of drug treatment outweigh risks of untreated disease. Because the uteroplacental circulation is maximally dilated and cannot autoregulate, decreasing maternal BP with drugs may abruptly decrease uteroplacental blood flow. Diuretics reduce effective maternal circulating blood volume; consistent reduction increases risk of fetal growth restriction. However, hypertension with renal insufficiency is treated even if hypertension is mild or moderate.

Recommendations for chronic and gestational hypertension are similar and depend on severity. However, chronic hypertension may be more severe, and the BP ranges in gestational diabetes often do not require treatment.

If hypertension is mild (140/90 to 150/100 mm Hg) and if BP is labile, reduced physical activity may decrease BP and improve fetal growth, making perinatal risks similar to those for women without hypertension. However, if these conservative measures do not decrease BP, many experts recommend drug therapy.

If hypertension is moderate (150/100 to 180/110 mm Hg), drug therapy is indicated. Women who are taking methyldopaSome Trade Names
ALDOMET
Click for Drug Monograph
, a β-blocker, a Ca channel blocker, or a combination before pregnancy may continue these drugs. However, ACE inhibitors and diuretics should be stopped once pregnancy is confirmed. Women must be taught to self-monitor BP and should have renal function testing every trimester. Fetal growth is monitored with monthly ultrasound examinations; antenatal testing begins at 32 wk. Delivery should be accomplished at 38 to 39 wk but may be done earlier if severe preeclampsia or fetal growth restriction is detected or if fetal testing is nonreassuring.

If hypertension is severe (≥ 180/110 mm Hg), immediate evaluation, including BUN and serum creatinine, creatinine clearance, 24-h urinary protein level, and funduscopy, is indicated. Risk of complications—maternal (progression of end-organ dysfunction or preeclampsia) and fetal (prematurity, growth restriction, stillbirth)—is increased significantly. If continuation of pregnancy is strongly desired despite the risk, several antihypertensives are often required. Hospitalization is also often required for much of the latter part of pregnancy. If the woman's condition worsens, pregnancy termination may be recommended.

Drugs: First-line drugs for hypertension during pregnancy include methyldopaSome Trade Names
ALDOMET
Click for Drug Monograph
, β-blockers, and Ca channel blockers. Initial methyldopaSome Trade Names
ALDOMET
Click for Drug Monograph
dose is 250 mg po bid, increased as needed to 2 g/day or sometimes more unless excessive somnolence, depression, and symptomatic orthostatic hypotension occur. The most commonly used β-blocker is labetalolSome Trade Names
NORMODYNE
TRANDATE
Click for Drug Monograph
(a β-blocker with some α₁-blocking effects), which can be used alone or with methyldopaSome Trade Names
ALDOMET
Click for Drug Monograph
when the maximum daily dose of methyldopaSome Trade Names
ALDOMET
Click for Drug Monograph
has been reached. Usual dose of labetalolSome Trade Names
NORMODYNE
TRANDATE
Click for Drug Monograph
is 100 mg bid to tid, increased as needed to a total daily dose of 2400 mg. Adverse effects of β-blockers include increased risk of fetal growth restriction, decreased maternal energy levels, and maternal depression. Extended-release nifedipineSome Trade Names
ADALAT
PROCARDIA
Click for Drug Monograph
, a Ca-channel blocker, may be preferred because it is given once/day (initial dose of 30 to 60 mg); adverse effects include headaches and pretibial edema.

Several classes of antihypertensives are usually avoided during pregnancy:

• ACE inhibitors are contraindicated because risk of fetal urinary tract abnormalities is increased.
• Thiazide diuretics can adversely affect the fetus and should be avoided during pregnancy if possible.
• Aldosterone antagonists (spironolactoneSome Trade Names
  ALDACTONE
  Click for Drug Monograph
  and eplerenoneSome Trade Names
  INSPRA
  Click for Drug Monograph
  ) should be avoided because they may cause feminization of a male fetus.

Last full review/revision December 2008 by Sean C. Blackwell, MD

Content last modified December 2008