Clinical Review

Controlling chronic hypertension in pregnancy

OBG Manag. 2006 February;18(2):56-55

References

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4. Sibai BM, Lindheimer M, Hauth J, et al. Risk factors for preeclampsia, abruptio placentae, and adverse neonatal outcomes among women with chronic hypertension. N Engl J Med. 1998;339:667-671.

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Fetal surveillance includes ultrasound, growth scans, and nonstress testing (TABLE 8).

Hospitalization is warranted if uncontrolled severe hypertension, preeclampsia, or evidence of fetal growth restriction develops, so that more frequent evaluation of maternal and fetal well-being can be performed.

Delivery is indicated if any of these complications develop at or beyond 34 weeks’ gestation. If there are none of these complications, consider delivery at 36 to 37 weeks after documenting fetal lung maturity.⁵

Postpartum care

Women with high-risk chronic hypertension are at risk for postpartum complications such as pulmonary edema, hypertensive encephalopathy, and renal failure.^10,11 These risks are heightened in women with target organ involvement, superimposed preeclampsia, or abruptio placentae.¹⁰

Blood pressure must be closely controlled for at least 48 hours after delivery. Intravenous labetalol or hydralazine can be used as needed, and diuretics may be appropriate in women with circulatory congestion and pulmonary edema.¹² Oral therapy may be needed to control blood pressure after delivery. In some women, it may be necessary to switch to a new agent such as an ACE inhibitor, particularly in women who had pregestational diabetes or cardiomyopathy.

All antihypertensive drugs are found in breast milk, although differences in the milk-to-plasma ratio do occur. The longterm effects of maternal antihypertensive drugs on breastfeeding infants has not been studied. However, methyldopa appears to be a reasonable first-line oral therapy (if it is contraindicated, use labetalol). Milk concentrations of methyldopa appear to be low and are considered safe. Beta-blockers (atenolol and metoprolol) are concentrated in breast milk, whereas labetalol or propanolol have low concentrations.^13,14 Concentrations of diuretics in breast milk are low, but may diminish milk production.¹³ Little is known about the transfer of calcium-channel blockers to breast milk, but there are no apparent side effects. ACE inhibitors and angiotensin II receptor antagonists should be avoided because of their effects on neonatal renal function, even though their concentrations in breast milk appear to be low.

The authors report no financial relationships relevant to this article.

TABLE 6

Acute and long-term drug treatment

DRUG	STARTING DOSE	MAXIMUM DOSE	COMMENTS
ACUTE TREATMENT OF SEVERE HYPERTENSION
Hydralazine	5-10 mg IV every 20 min	30 mg*
Labetalol	20-40 mg IV every 10-15 min	220 mg*	Avoid in women with asthma or congestive heart failure
Nifedipine	10-20 mg orally every 30 min	50 mg*
LONG-TERM TREATMENT OF HYPERTENSION
Methyldopa	250 mg BID	4 g/day	Rarely indicated
Labetalol	100 mg BID	2,400 mg/day	First choice
Atenolol	50 mg/day	100 mg/day	Associated with intrauterine growth restriction
Propanolol	40 mg BID	640 mg/day	Use with associated thyroid disease
Hydralazine	10 mg TID	100 mg/day	Use in cases of left ventricular hypertrophy
Nifedipine	10 mg BID	120 mg/day	Use in women with diabetes
Diltiazem	120-180 mg/day	540 mg/day
Thiazide diuretic	12.5 mg BID	50 mg/day	Use in salt-sensitive hypertension and/or congestive heart failure
			May be added as second agent
			Avoid if preeclampsia develops or intrauterine growth restriction is present
Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers	—	—	Do not use after 16-18 weeks
*If desired blood pressure levels are not achieved, switch to another drug.

TABLE 7

How to evaluate gravidas with chronic hypertension

POPULATION	RECOMMENDED TESTS
All	Urinalysis, urine culture and sensitivity 24-hour urine evaluations for protein Electrolytes Complete blood count Glucose tolerance test
Gravidas with longstanding hypertension, poor compliance, or poor control	Electrocardiogram Echocardiography Ophthalmologic evaluation Creatinine clearance

TABLE 8

Recommended antenatal testing

LEVEL OF RISK	TEST
Low (uncomplicated)	Ultrasound at 16–18 weeks to confirm gestational age/anatomy scan Ultrasound for fetal growth and fluid starting at 32–34 weeks Growth scan 37–38 weeks Nonstress testing weekly starting at 34 weeks Biophysical profile if nonstress test is nonreactive
High (complicated)	Ultrasound at 16–18 weeks to confirm gestational age/anatomy scan Start testing at 26–28 weeks with nonstress testing 1–2 times/week Biophysical profile if nonstress test is nonreactive Serial testing as needed