Abbreviated postpartum magnesium sulfate therapy for women with mild preeclampsia: a randomized controlled trial.

OBJECTIVE To determine whether women receiving 12-hour and 24-hour postpartum magnesium sulfate (MgSO4) therapy for mild preeclampsia have differing clinical courses. METHODS Consenting women with suspected mild preeclampsia were randomly assigned to 12 hours or 24 hours of MgSO4 postpartum therapy. Treatment was continued after the assigned time period if there was evidence of severe preeclampsia. The frequency of progression to severe disease and other outcomes were compared between study groups using the Fisher exact, chi2, and Student t tests where appropriate. RESULTS Between January 2001 and August 2004, 200 women were enrolled. The 12-hour and 24-hour groups were similar in age, parity, delivered gestational age, anesthesia, and mode of delivery, as well as for proteinuria and blood pressure. In the 12-hour group, MgSO4 treatment was extended in seven women (6.9%) for progression to severe disease versus one (1.1%) in the 24-hour group (P = .07). Women who developed severe disease had higher blood pressures at the first prenatal visit (140/78 versus 122/69, P < or = .02 for systolic and diastolic pressures), at the time of randomization (152/88 versus 135/78, P < or = .03 for systolic and diastolic pressures), and were more likely to have insulin-requiring diabetes (27.3% versus 4.4%, P = .03). No 12-hour patients required treatment beyond 24 hours postpartum. There were no seizures, MgSO4 toxicity, or intolerance in either group. CONCLUSION Twelve hours of postpartum MgSO4 therapy for mild preeclampsia is associated with infrequent disease progression and a clinical course similar to that with 24-hour therapy. Patients with chronic hypertension and insulin-requiring diabetes are at risk for progression to severe disease postpartum. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov, www.clinicaltrials.gov, NCT00344058 LEVEL OF EVIDENCE I.