There are huge doubts as to how long to keep postpartum magnesium sulfate. Studies demonstrating the usefulness for 24, 12 or 6 hours are of little evidence and do not take into account the use of magnesium sulphate before delivery. Termination of pregnancy is the best option to prevent eclampsia and magnesium sulphate has proven effective, but do not know the minimum effective dose.The investigators believe that if the patient has received less than 8 continuous hours of magnesium sulphate before delivery, maintain magnesium sulfate for 6 hours is as effective as keeping it for 24 hours.