Abbreviated Postpartum Magnesium Sulfate Therapy for Women with Mild Preeclampsia. A Randomized Controlled Trial

Preeclampsia complicates 5 to 8% of all deliveries. Standard treatment consists of management of hypertension, delivery, and administration of intravenous magnesium sulfate for 24 hours. Recently there has been interest in shortening the time for magnesium therapy in women at low risk of developing preeclampsia, in order to shorten the stay in the labor and delivery unit, decrease costs, and minimize the duration of magnesium-associated symptoms. The investigators prospectively compared the treatment of mild preeclampsia for 12 hours to treatment for 24 hours. Study patients were 34 weeks' gestation or more and had mild preeclampsia as defined by new onset blood pressure of 140 mm Hg or greater systolic and 90 mm Hg or greater diastolic, at least 1 + proteinuria, and the absence of symptoms or laboratory findings consistent with severe preeclampsia. The diagnosis was made either before or within two hours after delivery, before discharge from the labor and delivery unit. Magnesium sulfate was given as a 4 gram IV bolus followed by an infusion of 2 grams per hour, and IV fluids were maintained at a total rate of 125 ml per hour. Randomization was by computer-generated random number table distributed in blocks of 10. Study patients who were clinically stable at the end of their prescribed MgSO 4 infusion were sent to the postpartum ward, while those with continued hypertension or symptoms remained on labor and delivery for additional MgSO 4 therapy. Of a total of 322 patients with suspected mild preeclampsia, 204 were eligible and 200 were enrolled. Four patients were lost to follow up. The groups receiving either 12 or 24 hours of MGSO 4 were similar in terms of the severity of their preeclampsia and history of chronic hypertension or diabetes. One patient in the 24 hour group required additional MgSO 4 therapy. Seven in the 12 hour group required additional therapy, and 3 of these had chronic hypertension, three had diabetes, and two had both. Both groups tolerated the MgSO 4 well, and no patients experienced seizures or toxicity. The length of the postpartum stay was the same in both groups. These data indicate that selected women with mild preeclampsia can safely receive 12 hours of IV MgSO 4 therapy instead of 24 hours. Women with chronic hypertension or diabetes require 24 hours of therapy.