Chronic Hypertension in Pregnancy

Contributors:  Baylee Brown, DO; Sharon Keiser, MD

Updated:  July, 2023

Definition and background:

Chronic hypertension (CHTN): systolic blood pressure (SBP) >140 or diastolic blood pressure (DBP) >90 on 2 separate occasions at least 4 hours apart, diagnosed prior to pregnancy or before 20 weeks gestation or persisting longer than 12 weeks postpartum.

               Mild cHTN: SBP >140 and/or DBP >90

               Severe cHTN: SBP >160 and/or DBP >110

Chronic hypertension develops in 2% of pregnancies¹. Most patients have essential (primary) hypertension, 10% have a secondary cause (renal or endocrine). African Americans are significantly more likely to have cHTN and are three to five times more likely to have adverse outcomes. Pregnancy outcomes have been shown to be worse with uncontrolled high blood pressure. Until recently there was minimal data on treatment of mild cHTN in pregnancy as there was concern for poor fetal growth while on antihypertensives. According to the recent CHAP trial there was no significant difference in fetal growth when patients were treated for mild chronic hypertension. SMFM now recommends treatment of mild chronic hypertension with appropriate antihypertensive medication. Number needed to treat (NNT) was 14.7 to prevent one adverse outcome in CHAP trial.

Treatment with antihypertensives seems to significantly improve pregnancy outcomes⁶.  In pregnancy, BP nadirs at 14-28 weeks, thus if patient presents during this time with normal BP, then begins to have elevated blood pressure after 20 weeks, preeclampsia or gestational hypertension should be strongly considered as diagnosis.

• Relative contraindications to pregnancy: Persistent DBP ≥ 110, need for multiple antihypertensive agents, or creatinine ≥ 2mg/dL
• Strong contraindications to pregnancy: Prior cerebrovascular accident, myocardial infarction or cardiac failure

Risks of CHTN in Pregnancy

Maternal:

• worsening hypertension/superimposed preeclampsia
• placental abruption
• postpartum hemorrhage
• stroke
• renal failure
• cardiac failure
• gestational diabetes
• cesarean delivery

Fetal:

• miscarriage
• stillbirth
• neonatal death
• growth restriction
• prematurity
• congenital anomalies

Initial assessment

• Appropriate measurement of BP: sitting comfortably for 10 minutes, back supported, legs uncrossed, no caffeine or tobacco for 30 minutes, appropriate size cuff, arm at the level of the heart
• If new elevated blood pressure > 140 systolic or >90 diastolic, change cuff to appropriate size (if applicable) and recheck
• Baseline CBC, CMP and Protein-to-creatinine ratio (P:C).
• Proteinuria: if P:C ≥ 0.2 and <0.3 consider collecting 24 hr urine for protein and CrCl
• Renal function: serum creatinine, if ≥1.1 mg/dL repeat every trimester
• If longstanding hypertension (>5years) obtain EKG; if signs of left ventricular hypertrophy obtain echocardiogram
• Screening for secondary hypertension if: persistent hypertension on ≥2 medications, hypokalemia, creatinine > 1.1 mg/dL, or strong family history of kidney disease

Management

• Initiate antihypertensive if SBP ≥140 or DBP ≥90 (or both).
• Continue established regimen during pregnancy or change to a compatible pregnancy regimen if known chronic hypertension.
• Decrease/discontinue medications if SBP < 110 or DBP < 60, or MAP < 60
  • Mean Arterial Pressure = DBP + 1/3(SBP-DBP)
• Encourage exercise and smoking cessation.
• Initiate low-dose aspirin (162 mg daily at bedtime) ideally between 12 and 16 weeks EGA to help prevent early-onset, severe preeclampsia.  (Some benefit if started between 16 and 28 weeks EGA)
• If BP increases >32 weeks gestation, DO NOT start medication or titrate medications without a preeclampsia evaluation to prevent masking of superimposed preeclampsia
• Antenatal testing
  • Not on meds: Growth scans at 28 and 34 weeks, no other testing indicated
  • On meds: Growth scans q 4 weeks, initiate twice weekly testing starting at 32 weeks       

Timing of Delivery

• No medications: 39 weeks
• On antihypertensive medication: 37-39 weeks
• Superimposed preeclampsia without severe features: 37 weeks
• Superimposed preeclampsia with severe features: 34 weeks or at time of diagnosis if after 34 weeks

 

Superimposed Preeclampsia

• Occurs 20-50% of the time with underlying chronic hypertension, with earlier onset and higher severity
• Consider this dx when
  • new or worsening elevations in BP when compliant on medication, or
  • New or worsening BP elevations in a patient who has not required medication, after 20 weeks gestation with new or worsening proteinuria
• New onset headache, vision changes, right upper quadrant/epigastric pain, nausea/vomiting, hyperreflexia/clonus
• Obtain lab testing: CBC, CMP, urine P:C
• In the setting of severe range blood pressures, inpatient work up should be completed to differentiate chronic hypertension exacerbation versus superimposed preeclampsia, which includes serial blood pressures, CBC, CMP, P/C ratio, fetal monitoring
• Inpatient management from time of diagnosis until delivery if severe features and less than 34 weeks
• Antenatal testing starting at time of diagnosis (after 26 weeks)

Criteria for admission for further work up

• Blood pressure ≥160 systolic and/or >110 diastolic
• Other signs or symptoms of preeclampsia
• Non reassuring fetal tracing or fetal growth restriction (overall growth OR AC <10^th percentile)
• No reliable source of contact
• Multiple gestation
• Significant comorbidities: insulin-controlled diabetes, connective tissue disorders, sickle cell disease, maternal heart disease

Antihypertensive therapy

• Labetalol: start at 100-200 mg q 12hours, can titrate to 800 mg q 8hours
  • Adverse effects: dizziness, fatigue, orthostatic hypotension, nausea.
  • Avoid in patients with asthma, heart disease or congestive heart failure.
  • Avoid in patients with type 1 DM with reduced hypoglycemia awareness.
• Calcium channel blockers (Procardia, amlodipine): Procardia XL 30 mg QD, can titrate to 60 mg q12 hours, amlodipine 5-10 mg QD
  • Adverse effects: flushing, peripheral edema, orthostatic hypotension, and headache
  • Reflex tachycardia
• Methyldopa: 250 -1500 mg q12 hours
  • Adverse effects: sedation, hepatic dysfunction, hemolytic anemia
  • Less effective at controlling blood pressure
• Hydralazine (used in combination with other agents): 10-50 mg q8 hours
  • Adverse effects: tachycardia
• Diuretics (chlorthalidone/hydrochlorothiazide)
  • Theoretical risk of fetal growth restriction and oligohydramnios due to lack of volume expansion
  • Add if previous severe uncontrolled hypertension, benefit outweighs risk
• ACE/ARB: CONTRAINDICATED in pregnancy
  • Associated with fetal renal anomalies, oligohydramnios, pulmonary hypoplasia, calvarium abnormalities, growth restriction

Postpartum

• Resume pre-pregnancy regimen
• If new diagnosis during pregnancy, continue medication if BP remains ≥140 systolic or ≥90 diastolic prior to discharge from hospital
• Do not have to be normotensive prior to discharge
• Avoid methyldopa in postpartum period as it has been shown to worsen depression
• Schedule a BP check within 3-5 days of discharge from the hospital
• Refer to a PCP postpartum

References

1. American College of Obstetricians and Gynecologists. Hypertension in pregnancy: report of the American College of Obstetricians and Gynecologists’ Task Force on Hypertension in Pregnancy. Obstet Gynecol 2013; 122: 1122-31.
2. American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins — Obstetrics. ACOG practice bulletin no. 203: chronic hypertension in pregnancy. Obstet Gynecol 2019; 133(1):e26-e50.
3. Bateman BT, Bansil P, Hernandez-Diaz S, Mhyre JM, Callaghan WM, Kuklina EV. Prevalence, trends, and outcomes of chronic hypertension: a nationwide sample of delivery admissions. Am J Obstet Gynecol 2012; 206(2): 134.e1-8.
4. Hypertensive disorders. Cunningham F, & Leveno K.J., & Bloom S.L., & Dashe J.S., & Hoffman B.L., & Casey B.M., & Spong C.Y.(Eds.), (2018). Williams Obstetrics, 25e. McGraw Hill.
5. SMFM Publications Committee. SMFM statement: Antihypertensive therapy for mild chronic hypertension in pregnancy The Chronic Hypertension and Pregnancy trial. Am J Obstet Gynecol 2022; 227: 24-27.
6. Tita AT, Szychowski JM, Boggess K, et al. Treatment for mild chronic hypertension during pregnancy. N Engl J Med 2022; 307 (7): 663-664.