Diagnosis. Without documentation of elevated blood pressure before pregnancy, chronic hypertension can only be presumed. The vast majority of patients who present with elevated blood pressure before the twentieth week of gestation, however, have chronic hypertension. Signs of long-standing hypertension in the retina or other organ systems strongly suggest the diagnosis. Women with chronic hypertension are at high risk of developing superimposed preeclampsia manifest by worsening hypertension, diffuse edema, or proteinuria. In patients with severe labile hypertension, a search for underlying vascular, renal, or endocrine causes should be considered.
Management. Complicating cardiac, renal, neurologic, and retinal disease must be excluded in all women with chronic hypertension, ideally before pregnancy. Medications should be reviewed and, if necessary, changed appropriate for pregnancy. Use of low-dose aspirin at 60 to 80 mg/day has been advocated by some to decrease the likelihood of superimposed preeclampsia. Patients with mild hypertension not receiving medication are generally treated conservatively during pregnancy, with mild sodium restriction, increased bed rest, and daily home blood pressure measurements. Smoking must be eliminated. If blood pressure exceeds 140/100 mm Hg, oral antihypertensive medication is usually administered using the fewest number and safest drugs necessary to maintain diastolic blood pressure near 90 mm Hg. Lowering diastolic blood pressure consistently below 90 mm Hg is not desirable because uterine blood flow may be reduced and fetal growth impaired.
Methyldopa is currently the drug of choice in the United States for treating significant chronic hypertension during pregnancy. Hydralazine has also been used extensively, with no evidence of fetal compromise. Use of β-adrenergic blocking agents during pregnancy was originally condemned, particularly with respect to their effect on uteroplacental hemodynamics. Infrequent neonatal side effects include mild bradycardia and hypoglycemia. A number of prospective series using labetalol for treatment of chronic hypertension support its safety during pregnancy. The use of diuretics in pregnancy continues to be controversial. As long as maternal electrolytes remain normal, no detrimental effects have been observed in the fetus or neonate when diuretics have been initiated before pregnancy. Given the other alternatives available for treatment of hypertension during pregnancy, it is inadvisable to initiate diuretics during gestation except in the circumstance of cardiac decompensation. Although oral nifedipine can be an effective agent in the control of acute hypertension during pregnancy, there is little experience with long-term administration of calcium-blocking drugs during pregnancy. Therefore its widespread use to treat chronic hypertension throughout gestation awaits additional study. Angiotensin-converting enzyme (ACE) inhibitors have been associated with impairment of fetal growth, severe oligohydramnios, anatomic abnormalities, renal failure, and death in up to 20% of neonates when used in the second and third trimester. Women in their childbearing years treated for chronic hypertension should not be treated with ACE inhibitors unless adequate contraception can be ensured.
Maternal and Fetal Effects. Women with chronic hypertension during pregnancy are at risk for superimposed preeclampsia and abruptio placenta and for developing fetal intrauterine growth retardation. Development of these sequelae is more likely in women with long-standing severe hypertension and in those with preexisting cardiac or renal involvement, or in those with diastolic pressures greater than 110 mm Hg during the first trimester. Early documentation of fetal age is mandatory, with monthly ultrasound evaluation of growth and development in the second half of pregnancy. Weekly antepartum fetal evaluation is mandatory during the last 6 to 8 weeks of pregnancy, or earlier if poor fetal growth is noted. In circumstances of significant fetal growth retardation or suspicious antepartum fetal testing, delivery is indicated regardless of gestational age.
Hypertension without proteinuria or abnormal edema that develops late in gestation or in the puerperium is referred to as late or transient hypertension. Blood pressure normalizes by the tenth postpartum day. Often it may be difficult to differentiate transient hypertension from early preeclampsia. Almost half of the women with transient hypertension in pregnancy subsequently develop long-standing chronic hypertension.
Revision date: June 11, 2011
Last revised: by Amalia K. Gagarina, M.S., R.D.