What are the recommendations for managing hypertension in a pregnant patient taking lisinopril (angiotensin-converting enzyme inhibitor)?

Management of Hypertension in Pregnant Patients on Lisinopril

Lisinopril must be immediately discontinued in pregnant patients and switched to safer alternatives such as methyldopa, nifedipine, or labetalol due to severe fetotoxicity of ACE inhibitors. 1, 2

Risks of ACE Inhibitors in Pregnancy

ACE inhibitors like lisinopril are classified as Pregnancy Category D drugs and are strictly contraindicated during pregnancy due to:

• Severe fetotoxicity, particularly in the second and third trimesters 2
• Reduced fetal renal function 2
• Increased fetal and neonatal morbidity and mortality 2
• Oligohydramnios (can lead to fetal lung hypoplasia and skeletal deformations) 2
• Potential neonatal adverse effects including:
  • Skull hypoplasia
  • Anuria
  • Hypotension
  • Renal failure
  • Death 2

Immediate Management Steps

1. Discontinue lisinopril immediately upon confirmation of pregnancy 1, 2

2. Transition to pregnancy-safe antihypertensive medications:

   • First-line options:
     • Methyldopa (250-500 mg twice daily) 1
     • Labetalol (200-800 mg divided twice daily or more frequently) 1, 3
     • Nifedipine (30-60 mg extended-release once daily) 1, 3

3. Arrange for fetal assessment:

   • Serial ultrasound examinations to assess amniotic fluid volume 2
   • Monitor for signs of oligohydramnios 2
   • If oligohydramnios is detected, additional fetal testing may be appropriate based on gestational age 2

Blood Pressure Targets in Pregnancy

• For mild-to-moderate hypertension (140-160/90-109 mmHg): Treatment reduces risk of progression to severe hypertension by 50% 1
• For pregnant patients with diabetes and chronic hypertension: Target BP of 110-135/85 mmHg 1
• For severe hypertension (≥160/110 mmHg): Immediate intervention required with target BP <160/110 mmHg but not lower than 130/90 mmHg 3

Medication Selection Considerations

• Beta-blockers and CCBs appear superior to alpha-methyldopa in preventing preeclampsia 1
• Largest clinical experience is with:
  • Labetalol (beta-blocker)
  • Nifedipine (calcium channel blocker) 1
• Methyldopa has the longest safety record with infant follow-up (7.5 years) 1

Monitoring and Follow-up

1. During pregnancy:

   • Regular BP monitoring
   • Serial ultrasound examinations to assess fetal growth and amniotic fluid volume
   • Monitor for signs of preeclampsia (proteinuria, edema, headache, visual disturbances)

2. Postpartum:

   • Monitor BP closely for at least 24-72 hours 3
   • Review within 1 week if still requiring antihypertensives at discharge 3
   • Evaluation at 3 months postpartum to ensure BP, urine analysis, and laboratory tests have normalized 3

Special Considerations

• If the patient was inadvertently taking lisinopril during the first trimester, close monitoring with fetal ultrasound is advisable 1
• The risk of adverse outcomes is highest with second and third-trimester exposure 2
• For breastfeeding mothers, lisinopril should be avoided as it may be excreted in human milk 2

Common Pitfalls to Avoid

1. Delaying discontinuation of ACE inhibitors once pregnancy is confirmed
2. Inadequate fetal monitoring after ACE inhibitor exposure
3. Overly aggressive BP lowering which may compromise uteroplacental perfusion
4. Failure to monitor for preeclampsia, which occurs in 3.8% of pregnancies and accounts for 9% of maternal deaths in the US 1
5. Neglecting postpartum follow-up, as women with hypertension during pregnancy have increased long-term cardiovascular risk 3

By promptly discontinuing lisinopril and initiating appropriate antihypertensive therapy, the risks to both mother and fetus can be significantly reduced while maintaining adequate blood pressure control throughout pregnancy.