Taking a rational approach to hypertension in the pregnant patient

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COMMITTEE ON PRACTICE BULLETINS-OBSTETRICS Practice Bulletin #203: Chronic Hypertension in Pregnancy. American College of Obstetricians and Gynecologists. Obstet Gynecol 2019;133:e26-50. Full text of Practice Bulletin #203 is available to ACOG members at http://www.acog.org/Resources-and-Publications/Practice-Bulletins/Committee-on-Practice-Bulletins-Obstetrics/Chronic-Hypertension-Pregnancy

Chronic Hypertension in PregnancyChronic hypertension is present in 0.9-1.5% of pregnant women (1) and may result in significant maternal, fetal, and neonatal morbidity and mortality. The rate of maternal chronic hypertension increased by 67% from 2000 to 2009, with the largest increase (87%) among African American women. This increase is largely secondary to the obesity epidemic and increasing maternal age (1,2). The trend is expected to continue.

The purpose of this document is to clarify the criteria used to define and diagnose chronic hypertension before or during pregnancy, to review the effects of chronic hypertension on pregnancy and vice versa, and to appraise the available evidence for management options. The purpose of these revised best practice recommendations is to provide a rational approach to chronic hypertension in pregnancy based on new research and relevant pathophysiologic and pharmacologic considerations.

COMMENTARY

Taking a rational approach to hypertension in the pregnant patient

The new American College of Obstetricians and Gynecologists (ACOG) Practice Bulletin on chronic hypertension in pregnancy¹ replaces the prior ACOG task force hypertension in pregnancy report from 2013, which covered the full range of hypertensive diseases in pregnancy in an extremely thorough way.  However, several factors prompted a needed update with a dedicated focus on chronic hypertension in pregnancy, particularly the new recommendations issued by the American College of Cardiology (ACC) and the American Heart Association (AHA) on the diagnosis and management of hypertensive disease in adults.²

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Diagnosis

Chronic hypertension in pregnancy is defined as any one of the following:

• Hypertension diagnosed or present before pregnancy, whether or not a woman is on antihypertensive medication

• Elevated blood pressure prior to 20 weeks of gestation on two occasions at least 4 hours apart. For the purposes of this diagnosis, a threshold of 140 mm Hg systolic or 90 mm Hg diastolic or both is used.

The basic core of these recommendations is unchanged from the ACOG task force report. However, it is unclear how to align the recent ACC/AHA guidelines² with these pregnancy-related recommendations.  The ACC/AHA criteria for diagnosing hypertension in adults now classify blood pressure into four categories based on blood pressure results, with stage I hypertension (and recommendation for treatment) starting at a lower blood pressure threshold than we typically use for pregnancy, systolic blood pressure of 130 to 139 mm Hg or diastolic blood pressure of 80 to 89 mm Hg.

While there is no consensus on how to apply the ACC/AHA recommendations to pregnancy, there does not appear to be benefit to initiating antihypertensive medication during pregnancy or low-dose aspirin for preeclampsia prevention for women who meet criteria for stage I hypertension during pregnancy based on a recent secondary analysis of a multicenter randomized controlled trial.³  However, data are limited on outcomes and preventative measures in women with stage I chronic hypertension.  Therefore, according to ACOG, it is reasonable to continue managing patients who met the criteria for a diagnosis of hypertension based on ACC/AHA recommendations (including stage I hypertension) prior to pregnancy as chronically hypertensive during pregnancy.

The bulletin also addresses another hot diagnosis: white coat hypertension.  Women with white coat hypertension are hypertensive during office visits but otherwise normotensive. They should be observed carefully during pregnancy as they are at increased risk of developing preeclampsia and gestational hypertension.⁴ Ambulatory blood pressure monitoring may be helpful when making decisions about starting antihypertensive medications in these patients.

Risks

Chronic hypertension carries risks to both mother and fetus during pregnancy, with severe and uncontrolled hypertension associated with the highest risks for both. For the mother, there is an increased risk of mortality, cerebrovascular accidents, pulmonary edema, and renal failure; however, the absolute risk of these complications remains low. Fetal risks include increased risk of stillbirth or perinatal death, fetal growth restriction, preterm birth (mostly ascribed to an increase in indicated preterm deliveries), and congenital anomalies, with the highest risk of these abnormalities correlating with presence of maternal end-organ damage.

Prepregnancy management

The prepregnancy period remains the ideal time to initiate care-to look for end-organ damage, assess medications, look for signs of secondary hypertension (such as underlying renal, endocrine or vascular disease) and refer the patient for evaluation if needed, discuss the role of low-dose aspirin for preeclampsia prevention, improve blood pressure control prior to conception, and modify other risk factors that often are seen in conjunction with chronic hypertension, such as diabetes mellitus and obesity.

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Antepartum management

Antepartum management is targeted toward blood pressure control, reducing risk of complications such as preeclampsia, identifying maternal and fetal complications early, and determining optimal timing of delivery.  At the first prenatal visit, baseline labs should be sent, including serum aspartate aminotransferase and alanine aminotransferase, serum creatinine, serum electrolytes, blood urea nitrogen, complete blood count, and spot urine protein/creatinine ratio or 24-hour urine for total protein and creatinine.  Electrocardiogram or echocardiogram should be ordered as appropriate.  Patients with either chronic hypertension or white coat hypertension should be advised to initiate low-dose aspirin (81 mg daily) between 12 and 28 weeks (optimally before 16 weeks) and continue it until delivery for prevention of preeclampsia.

For patients not already on an antihypertensive medication, antihypertensive therapy should be initiated when the systolic blood pressure is 160 mm Hg or more, diastolic 110 mm Hg, or both.  The target range is 120 to 160 mm Hg systolic and 80 to 110 mm Hg diastolic.  Lower targets may be desirable in women with signs of end-organ damage.

Which antihypertensives are best during pregnancy?  

Nifedipine and labetalol are recommended above other antihypertensive medications.  Methyldopa may be used but appears to be less effective than nifedipine or labetalol in achieving blood pressure control. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are generally not recommended due to the risks of fetal renal dysgenesis and calvarial hypoplasia. Other medications, such as conidine and prozosin, can be considered as second-line agents. Acute treatment of severely elevated blood pressure can be achieved using intravenous (IV) labetalol, IV hydralazine, and/or oral nifedipine.  The Practice Bulletin provides several different algorithms for achieving urgent blood pressure control.  Care should be taken to avoid overcorrection of blood pressure leading to hypotension, which can affect uterine perfusion.

Fetal surveillance

Third-trimester ultrasound to assess fetal growth is advised in women with chronic hypertension. In terms of additional evaluation such as subsequent growth ultrasounds or fetal surveillance with nonstress testing or biophysical profiles, the Practice Bulletin does not make a solid recommendation due to limited data.

Timing of delivery

Timing of delivery depends on whether a patient is on antihypertensive medication and the degree of blood pressure control.  For all patients, delaying delivery later than 39 0/7 weeks should only be considered after a careful evaluation of the risks and benefits.

• Chronic hypertension not on antihypertensive medication:  not earlier than 38 0/7 weeks

• Chronic hypertension on antihypertensive medication with good control:  not earlier than 37 0/7 weeks

• Chronic hypertension with superimposed preeclampsia without severe features:  at 37 0/7 weeks; if at a later gestational age than 37 0/7 weeks, then upon diagnosis.

• Chronic hypertension with superimposed preeclampsia with severe features:  not later than

• 34 0/7 weeks; if at a later gestational age than 34 0/7 weeks, then upon diagnosis.

Immediate delivery after maternal stabilization is recommended if any of the following are present at any gestational age in women with superimposed preeclampsia:  uncontrollable severe hypertension, eclampsia, pulmonary edema, disseminated intravascular coagulation, new or worsening renal insufficiency, placental abruption, or abnormal fetal testing.

Intrapartum management

• Fetal monitoring: Continuous fetal monitoring during labor is advised in women with chronic hypertension at higher risk of adverse outcomes (e.g., those who requre any blood pressure control or with other short-term or long-term sequelae).

• Axial anesthesia: Axial anesthesia is safe even in the setting of severe hypertension. Unless contraindicated by thrombocytopenia, it should be used for cesarean delivery as general anesthesia may pose higher risks for women with severe hypertension.

Postpartum management

A patient’s blood pressure should be evaluated in the first 1 to 2 weeks after delivery, either with an early outpatient office visit or with home blood pressure monitoring. Target blood pressure is systolic blood pressure of 150 mm Hg or less and diastolic blood pressure of 100 mm Hg or less. The patient can be maintained on the medication used in pregnancy or she can be transitioned back to her pre-pregnancy medication.  Medications such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are compatible with breastfeeding.  NSAID use appears to be safe in postpartum patients with chronic hypertension. Methyldopa should be avoided because it often can be associated with depression.

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Unresolved controversies

Diagnosing superimposed preeclampsia:  Up to 20% to 50% of women with chronic hypertension develop superimposed preeclampsia.  Diagnosing superimposed preeclampsia in patients with chronic hypertension can be a challenge.  It can be difficult to determine whether a surge in blood pressure represents worsening chronic hypertension or superimposed preeclampsia.  ACOG indicates that laboratory testing can be helpful in distinguishing between the two by evaluating platelet count, liver function tests, and uric acid levels.

What’s new?

ACOG recommends an individualized approach in considering who meets a diagnosis of chronic hypertension.  Women diagnosed with stage I hypertension prior to pregnancy may be managed as chronic hypertensives in pregnancy even though they don’t meet the threshold of 140 mm Hg systolic or 90 mm Hg diastolic.

White coat hypertension is associated with an increased risk of adverse obstetrical outcomes and merits close observation at minimum with ambulatory blood pressure monitoring. 

Women with a diagnosis of chronic hypertension should be started on low-dose aspirin (81 mg daily) between 12 and 28 weeks (optimally befoe 16 weeks) to be continued until delivery. While women with stage I chronic hypertension as defined by ACC/AHA guidelines may be managed as chronically hypertensive during pregnancy, data are limited on outcomes and interventions to reduce the risk of preeclampsia, and further research is necessary to define optimal care.

Recommendations for timing of delivery depend on whether a patient is on antihypertensive medication, degree of blood pressure control, and presence or absence of superimposed preeclampsia. Many women with chronic hypertension now meet criteria for early term delivery.

Disclosures:

The author reports no potential conflicts of interest with regard to this article.

References:

ACOG ABSTRACT REFERENCES

• Bateman BT, Bansil P. Hernandez-Diaz S, Mhre JM, Callaghan WM, Kuklina EV. Prevalence, trends, and outcomes of chronic hypertension: a nationwide sample of delivery admissions. Am J Obstet Gynecol 2012;206:134.e1-8

• Martin JA, Hamilton BE, Ventura SJ, Osterman MJ, Kirmeyer S, Mathews TJ, et al. Births: final data for 2009. Natl Vital Stat Rep 2011;60:1-70.

COMMENTARY REFERENCES

• Chronic hypertension in pregnancy. ACOG Practice Bulletin No. 203. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2019;133:e26-e50.

• Whelton PK, Carey RM, Aranow WS, Casey DE Jr., et al.  2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults:  a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines.  J Am Coll Cardiol. 2018;71:e127-248.

• Sutton EF, Hauspurg A, Caritis SN, Powers RW, Catov JM.  Maternal outcomes associated with lower range stage I hypertension [preprint].  Obstet Gynecol. 2018.

• Brown MA, Mangos G, Davis G, Homer C.  The natural history of white coat hypertension during pregnancy.  BJOG. 2005;112:601-606