INCLUSION CRITERIA:

• Singleton or di-chorionic twin gestation.

• Gestational age at randomization from 23 weeks 0 days through 35 weeks 6 days based on clinical information and evaluation of the earliest ultrasound

• Diagnosis of gestational hypertension or preeclampsia without severe features within 10 days prior to randomization.

  • Gestational hypertension or preeclampsia is defined as new onset systolic blood pressure 140-159 or diastolic blood pressure 90-109 (or both) on two occasions at least four hours apart on or after 20 weeks 0 days gestation with normal end-organ labs, with or without proteinuria.
  • Blood pressure measurements used for the diagnosis must occur during a formal clinical assessment in the outpatient, inpatient, or emergency care setting and be documented in the medical record. The diagnosis is made on the date of the second qualifying blood pressure.
  • At least 1 elevated blood pressure (systolic blood pressure 140-159 and/or diastolic blood pressure 90-109) must be documented at the recruitment site

EXCLUSION CRITERIA:

• Known allergy or hypersensitivity to both labetalol and nifedipine ER

• Two blood pressure measurements ≥ 140/90 at least 4 hours apart prior to 20 weeks 0 days in the current pregnancy

• History or current use of anti-HTN medication defined as any of the following:

  • Prescribed anti-HTN medication for the indication of lowering blood pressure within 12 months prior to conception or prior to 20 weeks 0 days in the current pregnancy. Use during a prior pregnancy and through 12 weeks postpartum, or use for stage 1 chronic hypertension is not an exclusion.
  • Current use of anti-HTN medication. Participants on anti-HTN medication for the purpose of treating non-severe hypertensive disorders of pregnancy, or for indications other than hypertension, who are willing to go through a 48 hour washout before randomization would be eligible.

• High-risk co-morbidities for which treatment at a lower blood pressure level (i.e., below the standard cutoff of 160/110) may be indicated

  • Chronic kidney disease including any of the following lab values prior to 20 weeks gestation: proteinuria ≥ 300mg/24 hr, clean catch protein creatinine ratio ≥ 0.3, or serum creatinine >1.1
  • Cardiac disorders including cardiomyopathy, angina, and coronary artery disease
  • Prior stroke
  • Retinopathy
  • Sickle cell disease

Preeclampsia with severe features defined as any of the following:

• Severe hypertension defined as new onset systolic blood pressure ≥ 160 or diastolic blood pressure ≥ 110 on two occasions at least 4 hours apart (unless antihypertensive medication is initiated before this time) on or after 20 weeks 0 days gestation.

• Severe features of preeclampsia as evidenced by end organ damage defined as any of the following on or after 20 weeks 0 days gestation:

  • Thrombocytopenia defined as a platelet count <100,000
  • Renal insufficiency defined as a serum creatinine >1.1 mg/dL or a doubling of the concentration in the absence of other renal disease
  • Impaired liver function defined as an elevated blood concentration of liver transaminases to twice normal concentration, or by severe persistent right upper quadrant or epigastric pain
  • Pulmonary edema
  • New onset headache unresponsive to medication and not accounted for by alternative diagnoses
  • Visual disturbances

• Eclampsia

  • Oligohydramnios defined as a maximum vertical pocket (MVP) <2 cm or an amniotic fluid index (AFI) < 5 cm
  • Fetal growth restriction defined as estimated fetal weight < 5th percentile, or fetal growth restriction <10th percentile (estimated fetal weight <10th percentile or abdominal circumference < 10th percentile) with abnormal umbilical artery dopplers (elevated (S/D ratio >95th percentile for gestational age), absent or reversed end diastolic flow)
  • Known fetal genetic disease or major malformations
  • Fetal demise or planned termination of pregnancy.
  • Planned indicated delivery prior to 37 weeks 0 days
  • Participation in another interventional study that influences the primary outcome in this study. This may not apply to comparative effectiveness studies evaluating treatments that are available and used as part of clinical practice. Such cases will be adjudicated by the Concurrent Research Committee and Protocol Subcommittee.
  • Plan to deliver at a non-participating site
  • Participation in this trial in a previous pregnancy