To determine if nifedipine and enalapril will have better blood pressure control in the postpartum setting compared to nifedipine and labetalol.

The primary objective is to assess the efficacy of enalapril on hypertension as a second line agent compared to labetalol in the postpartum period. This is a pragmatic, unblinded, randomized trial of postnatal patients with hypertension who are on nifedipine postpartum and require a second oral agent. Patients will be evaluated for eligibility and consented when they require initiation of a single oral antihypertension agent, if they require IV antihypertensive therapy, or if they are on a single oral antihypertensive medication intrapartum. After consenting for the study, patients will be initiated on extended release nifedipine 30 mg daily as the primary drug for treatment and increased to a maximum dose of 60 mg twice daily prior to starting a second agent. Nifedipine was chosen as the universal first line agent due to its longevity and diuretic properties. Medication up titration and initiation of a second antihypertensive agent will occur at the discretion of the treatment team. Medication adjustments are recommended when the majority (>50%) of recorded blood pressures are greater than 140 mm Hg systolic or 90 mm Hg diastolic during a 24-hour time period. This threshold was chosen based on our knowledge that higher systolic blood pressures are associated with increased cardiovascular outcomes. Women requiring an additional medication for treatment of hypertension will be randomly assigned to receive enalapril 5 mg twice daily or labetalol 200 mg twice daily for concomitant therapy.

Blood pressures will be analyzed at 24 hours after initiation of a second oral agent, 3 days following hospital discharge, 2 weeks postpartum and 6 weeks postpartum. Need for IV antihypertensive agents and an additional third oral agent will be reviewed. As per standard of care, participants will be asked to monitor their blood pressure (BP) at home twice daily and keep their own blood pressure log to share with their outpatient provider. Patients are instructed to notify their outpatient provider of elevated blood pressure readings according to the Postpartum Hypertension Information Sheet that will be provided to all study participants.

Inclusion Criteria:

• Postpartum women aged 18 years or older
• Clinical diagnosis of hypertensive disorder in pregnancy (gestational hypertension, chronic hypertension, preeclampsia with or without severe features)
• Taking Nifedipine 60 mg every 12 hours for blood pressure control
• Persistently elevated blood pressure at/above 140/90 mmHg in a 24-hour time period or have one or more severe range blood pressure at/above 160/110 mmHg requiring a second antihypertensive medication
• English speaking

Exclusion Criteria:

• Taking ≥2 antihypertensive agents during pregnancy
• Heart block
• Heart rate <60 or >120 beats per minute
• Heart failure
• Creatinine >1.5 mg/dL
• Renal artery stenosis
• Active connective tissue disease
• Cerebrovascular accident
• Failed treatment or contraindications to nifedipine, enalapril or labetalol

Postnatal women