Chronic Hypertension in Pregnancy
WHEC Practice Bulletin and Clinical Management Guidelines for healthcare providers. Educational grant provided by Women's Health and Education Center (WHEC).
Chronic hypertension occurs in up to 5% of pregnant women. This complication may result in significant maternal, fetal, and neonatal morbidity and mortality. According to the National High Blood Pressure Education Program Working Group in High Blood Pressure in Pregnancy (1), chronic hypertension is defined as hypertension present before the 20th week of pregnancy or hypertension present before pregnancy. The blood pressure (BP) criteria used to define hypertension are a systolic pressure of >140 mm Hg, a diastolic pressure of >90 mm Hg.
The purpose to this document is to review the effects of chronic hypertension on pregnancy, to clarify the terminology and criteria used to define and diagnose it during pregnancy, and to review the available evidence for treatment options. Chronic hypertension complicates pregnancy and is associated with several adverse outcomes, including premature birth, intrauterine growth restriction (IUGR), fetal demise, placental abruption, and cesarean delivery (3). An additional diagnostic complication may arise in women with hypertension who begin prenatal care after 20 weeks of gestation.
Criteria for diagnosis of chronic hypertension in pregnancy are:
- Mild: Systolic blood pressure >140 mm Hg
Diastolic blood pressure > 90 mm Hg
- Severe: Systolic blood pressure > 180 mm Hg
Diastolic blood pressure > 110 mm Hg
- Use of antihypertensive medications before pregnancy
- Onset of hypertension before 20th week of gestation
- Persistence of hypertension beyond the usual postpartum period
In order to reduce inaccurate reading, an appropriate size cuff should be used (length 1.5 times upper arm circumference or a cuff with a bladder that encircles 80% or more of the arm). Pressure should be taken with the patient in an upright position, after 10 minutes or longer rest period. For patients in the hospital, the blood pressure can be taken with either the patient sitting up or in the left lateral recumbent position with the patient's arm at the level of the heart. The patient should not use tobacco or caffeine for 30 minutes preceding the measurement. Although validated electronic devices can be used, a mercury sphygmomanometer is preferred.
An additional diagnostic complication may arise in women with chronic hypertension who begin prenatal care after 20 weeks of gestation. A physiologic decrease in blood pressure normally occurs early in the second trimester, and may be exaggerated in women with chronic hypertension. This decrease my lead to an erroneous assumption that the blood pressure is normal at this stage of gestation. By the third trimester, blood pressure usually returns to its pre-pregnancy level. Women with preeclampsia also may have hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. However, the development of superimposed preeclampsia in pregnant women with chronic hypertension is relatively common and is often difficult to diagnose. The acute onset of proteinuria and worsening hypertension in women with chronic hypertension is suggestive of superimposed preeclampsia.
Effects of Chronic Hypertension on Pregnancy:
The most common adverse outcomes are: premature birth, intrauterine growth restriction (IUGR), fetal demise, placental abruption, and cesarean delivery. The incidence of these potential adverse effects is related to the degree and duration of hypertension and to the association of other organ system involvement or damage. As many as one third of women with severe chronic hypertension may have a small-for-gestational-age (SGA) infant, and two thirds may have a preterm delivery. Perinatal mortality of 2-4 times more than the general population is noted in many studies. The risk of placental abruption is about double. The association between chronic hypertension and preeclampsia, preterm, SGA, or low-birth-weight infants when compared with normotensive women or the general obstetric patient, the incidence is about triple. The risk of these complications was increased even in the absence of superimposed preeclampsia, although the absolute increased risk from mild hypertension is difficult to predict.
Effects of Pregnancy on Hypertension:
Several physiologic changes occur in pregnant women that can affect chronic hypertension. One of the most significant changes is the increase in blood volume, which may further burden an already stressed heart and along with the decrease in colloid oncotic pressure, may lead to cardiac decompensation. Another important change is the physiologic decrease in blood pressure, which begins by the end of the first trimester and reaches its lowest level at 16-18 weeks of gestation. This change can mask either the course or the detection of chronic hypertension in early pregnancy. Besides superimposed preeclampsia or eclampsia, pregnancy complicated by chronic hypertension (especially if severe) may be associated with worsening or malignant hypertension, central nervous system hemorrhage, cardiac decompensation, and renal deterioration or failure.
Evaluation and Clinical Considerations:
Ideally, a woman with chronic hypertension should be evaluated before conception to ascertain potentially reversible causes and possible end-organ involvement (eg, heart or kidney). The age of onset, results of previous evaluation, severity and duration of hypertension, and physical examination are important determinants of which clinical tests may be useful. Women who have had hypertension for several years are more likely to have cardiomegaly, ischemic heart disease, renal involvement, and retinopathy. Tests usually include electrocardiography, echocardiography, ophthalmologic examination and renal ultrasonography. Women with significant left ventricular hypertrophy secondary to hypertension may experience cardiac decompensation and heart failure as pregnancy progresses. Women with significant renal disease (serum creatinine >1.4 mg/dl) may experience deterioration of renal function, although it may be difficult to separate the effects of pregnancy from the disease process. However, most pregnant women with mild chronic hypertension have uneventful pregnancies with no end-organ involvement.
In pregnant women with known essential hypertension (primary hypertension or hypertension not secondary to underlying renal or adrenal disease), baseline laboratory evaluations that may prove clinically useful include tests of renal function such as serum creatinine, blood urea nitrogen (BUN), and 24 hour urine evaluation for total protein and creatinine clearance. This initial laboratory assessment is important in identifying women with underlying renal disease because this complication may adversely affect pregnancy outcome. The subsequent development of proteinuria in a woman with essential hypertension also may be helpful in identifying the development of superimposed preeclampsia. As pregnancy progresses, other laboratory tests - in addition to repeating those mentioned previously - may be clinically useful in evaluating worsening renal disease and in diagnosing superimposed preeclampsia. These include liver function tests, hemoglobin/hematocrit evaluation, and platelet count. It has been reported that the random protein-creatinine ratio may be useful for the quantitation of proteinuria during pregnancy.
Although an elevated serum uric acid level represents a useful confirmatory test for the diagnosis of preeclampsia, it is very poor predictive value among patients without preexisting hypertension. Serum uric acid level of >5.5 mg/dl could identify women with an increased likelihood of having superimposed preeclampsia.
Distinguishing features from preeclampsia when the woman presents late in pregnancy:
It is often difficult, if not impossible, to distinguish worsening chronic hypertension from superimposed severe preeclampsia, especially when the patient presents late in pregnancy. In the woman with chronic hypertension and renal disease, it may not be possible to distinguish between two entities. If the same woman has only hypertension without proteinuria and no symptoms of preeclampsia, such as headache, epigastric pain, or scotomata, the diagnosis may be more difficult. However, the vast majority of young, nulliparous women presenting with hypertension for the first time during late pregnancy will have preeclampsia. In addition to testing for proteinuria, other tests that may be helpful include hemoglobin and hematocrit evaluation, platelet count, and liver function tests. These latter tests are useful in the diagnosis of the HELLP syndrome (4). Oliguria and an elevated hemoglobin / hematocrit level usually indicate hemo-concentration -- more indicative of preeclampsia. Serum creatinine levels also may be elevated in women with preeclampsia.
Women with mild hypertension (140-179 mm Hg systolic or 90-109 mm Hg diastolic pressure) generally do well during pregnancy and do not, as a rule, require antihypertensive medication. There is, to date, no scientific evidence that antihypertensive therapy will improve perinatal outcome. As suggested by the National High Blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy, therapy could be increased or reinstituted for women with blood pressures exceeding 150-160 mm Hg systolic or 100-110 mm Hg diastolic (1). In women with severe chronic hypertension (systolic pressure >180 mm Hg or diastolic pressure >110 mm Hg), antihypertensive therapy should be initiated or continued.
Although there are numerous antihypertensive agents that have been used for the chronic hypertension during pregnancy, methyldopa has been commonly used. It is preferred by most practitioners and appears to be relatively safe. Methyldopa appears to have limited effects on uteroplacental blood flow. (2)
Labetalol, a combined alpha- and beta-blocker, also can be used during pregnancy as an alternative to methyldopa. Calcium-channel blockers or antagonists also have been used with limited experience. Diuretics also have been used to treat chronic hypertension, but there has been concern regarding the potential effect of these medications on normal blood volume expansion associated with pregnancy. The Working Group concluded, "If diuretics are indicated, they are safe and efficacious agents that can markedly potentiate the response to other antihypertensive agents and are not contraindicated in pregnancy except in settings in which uteroplacental perfusion is already reduced (preeclampsia and IUGR).
Angiotensin-converting enzyme (ACE) inhibitors are contraindicated during the second and third trimesters of pregnancy. The teratogenic risk factors of ACE inhibitors are associated with severely underdeveloped calvarial bone, renal failure, oligohydramnios, anuria, renal dysgenesis, pulmonary hypoplasia, IUGR, fetal death, neonatal renal failure, and neonatal death. Fetal risks with ACE inhibitors depend on the timing and dose. Its use in first trimester (before renal tubular function begins) has not been associated with an increase in birth defects.
Fetal surveillance in Pregnancy: the testing should be individualized and based on clinical judgment and on the severity of the disease. Most appropriate fetal surveillance tests commonly used are non-stress test (NST), biophysical profile (BPP), modified BPP, CST and Doppler velocimetry. The interval and timing of testing in women with chronic hypertension should be individualized. Most of the increased morbidity associated with this condition is secondary to superimposed preeclampsia or IUGR. The general recommendation is that baseline ultrasonography should be obtained at 18-20 weeks of gestation and that ultrasonography should be repeated at 28-32 weeks of gestation and monthly thereafter until delivery to monitor fetal growth. If growth restriction is detected or suspected, fetal status should be monitored frequently with NST or BPP.
Labor and Delivery:
Pregnant patients with uncomplicated chronic hypertension of mild degree generally can be delivered vaginally at term; most have good maternal and neonatal outcomes. Cesarean delivery should be reserved for other obstetric indications. Women with hypertension during pregnancy and a prior adverse pregnancy outcome (stillbirth) may be candidates for earlier delivery after documentation of fetal lung maturity. Women with severe chronic hypertension during pregnancy most often either deliver prematurely or have to be delivered prematurely for fetal or maternal indications. Delivery should be considered in all women with superimposed severe preeclampsia at or beyond 28 weeks of gestation and in women with mild superimposed preeclampsia at or beyond 37 weeks of gestation.
Intrapartum Concerns: the majority of pregnant women with chronic hypertension have uncomplicated mild hypertension and can be managed in the same way as a normal, non-hypertensive women during the intrapartum period. Women with severe hypertension may require antihypertensive medications for acute elevation of blood pressure. It is generally recommended that antihypertensive medications be given to women with preeclampsia for systolic blood pressure of >160 mm Hg or diastolic blood pressure of 105-110 mm Hg or greater. Women with chronic hypertension complicated by significant cardiovascular or renal disease require special attention to fluid load and urine output because they may be susceptible to fluid overload with resultant pulmonary edema.
Analgesia and Anesthesia in labor: it is reasonable to conclude from various studies, that regional anesthetic techniques are safe and are used in women with severe hypertension; clinicians with specialized training in obstetric anesthesia should be available. General anesthesia may pose a risk in pregnant women with severe hypertension or superimposed preeclampsia. Intubation and extubation may be associated with acute and significant elevations in blood pressure and an agent such as Labetalol usually is given acutely to minimize this effect. Ketamine, because of its association with hypertension, in not considered first line of therapy, for the induction of general anesthesia. Magnesium sulfate should be used for women with superimposed severe preeclampsia to prevent seizures.
Intrapartum concerns unique to pregnant women with chronic hypertension:
The majority of pregnant women with chronic hypertension have uncomplicated mild hypertension and can be managed the same as normal, non-hypertensive women during the intrapartum period. In contrast, women with severe hypertension or hypertension that is complicated by cardiovascular or renal disease may present special problems during the intrapartum period. Women with severe hypertension may require antihypertensive medications for acute elevation of blood pressure. Although no well-designed studies specifically address the treatment of severe chronic hypertension during the intrapartum period, it is generally recommended that antihypertensive medications be given to women with preeclampsia for systolic blood pressure of >160 mmHg or diastolic blood pressure of 105-110 mmHg or greater (2)(5). Women with chronic hypertension complicated by significant cardiovascular or renal disease require special attention to fluid load and urine output because they may be susceptible to fluid overload with resultant pulmonary edema. There are sufficient data to address the benefits and potential harm of central invasive hemodynamic monitoring in women with pregnancy related hypertension (6).
High pre-pregnancy body mass index (BMI) and excessive gestational weight gain are associated with increased risk for hypertensive disorders in pregnancy. Few risk factors for pregnancy-related hypertensive disorders are modifiable. Recent evidence suggests BMI and maternal weight gain may be important factors (7). Hypertensive disorders of pregnancy are associated with maternal, fetal, and neonatal morbidity and mortality. Studies to date indicate a higher risk for preeclampsia among Latina women than non-Latina white women, although findings have varied among different Latina subgroups (8). High pre-pregnancy BMI (>29.0 kg/m2) may increase the risk for hypertensive disorders of pregnancy. Excessive gestational weight gain as defined by the Institute of Medicine may increase risk for hypertensive disorders in pregnancy. Women should be encouraged to maintain a pre-pregnancy BMI within established guidelines for healthy BMI and to avoid excessive weight gain in pregnancy.
Women with chronic hypertension should be evaluated for potentially reversible etiologies, preferably prior to pregnancy, and women with long-standing hypertension should be evaluated for end-organ disease, including cardiomegaly, renal insufficiency, and retinopathy. Methyldopa and Labetalol are first line of antihypertensive agents used during pregnancy. ACE inhibitors and beta-blocker atenolol are contraindicated during pregnancy. It is often difficult, if not impossible, to distinguish worsening chronic hypertension from superimposed severe preeclampsia, especially when the patient presents late in pregnancy.
- U.S. Department of Health and Human Services
High Blood Pressure in Pregnancy
- Centers for Disease Control and Prevention (CDC)
About High Blood Pressure
- Report of the National High Blood Pressure Education Program Working Group in High Blood Pressure in Pregnancy. Am J Obstet Gynecol 2000; 183: S1-S22 (Level III)
- Agency for Healthcare Research and Quality Management of chronic hypertension during pregnancy. Evidence Report/Technology Assessment no. 14. AHRQ Publication No. 00-E011. Rockville, Maryland: AHRQ, 2000 (Level III)
- Ferrer RL, Sibai BM, Mulrow CD et al. Management of mild chronic hypertension during pregnancy: a review. Obstet Gynecol 2000;96:849-860 (Level III)
- ACOG Practice Bulletin. Chronic hypertension in pregnancy. Number 29, July 2001
- Tanaka M, Jaamaa G, Kaiser M et al. Racial disparity in hypertensive disorders of pregnancy in New York State: a 10-year longitudinal population-based study. Am J Public Health 2007;97:163-170
- Callaghan WM, Mackay AP, Berg CJ. Identification of severe maternal morbidity during delivery hospitalizations, United States, 1991-2003. Am J Obstet Gynecol 2008;199:133.e1-e.8
- Ogden CL, Carroll MD, Flegal KM et al. High body mass index for age among US children and adolescents, 2003-2006. JAMA 2008;299:2401-2405
- Fortner RT, Penelope P, Solomon CG et al. Pre-pregnancy body mass index, gestational weight gain, and risk of hypertensive pregnancy among Latina women. Am J Obstet Gynecol 2009;200:167.e1-167e.7
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