Slow enrollment

The purpose of this study is to understand if administration of a personalized dose of the anti-hypertensive medication, labetalol, based on patient's history of preexisting hypertension, will be more effective at controlling severe hypertension during pregnancy, compared to the current standard dosing.

The investigators seek to asses the effect of preexisting hypertension on the patient's response to treatment for severe hypertension in preeclampsia with severe features. The investigators hypothesize that successive administration of 40-60-80 mg of labetolol will reduce time to blood pressure control versus the standard dosing, 20-40-80 mg labetolol, recommended by the American College of Obstetricians and Gynecologists in 2015.

Inclusion Criteria:

• Age ≥ 18 years
• Gestational age ≥ 24 weeks
• Singleton gestation
• Chronic hypertension as defined as two elevated blood pressures (SBP ≥ 140mmHg and/or DBP ≥ 90mmHg) at least 4 hours apart before 20 weeks gestation

Exclusion Criteria:

• Known allergic reaction to labetalol
• Persistent mild-moderate asthma (≥ 2 rescue inhaler uses per week in the previous month)
• Obstructive airway disease
• Bradycardia < 70 beats/min
• Heart block > 1st degree or history of heart failure

The principle investigator and outcomes assessor are masked to group assignment.