Magnesium sulphate more than halves the risk of eclampsia, and probably reduces maternal death. There is no clear effect on outcome after discharge from hospital. A quarter of women report side effects with magnesium sulphate.
A randomised controlled trial of intravenous magnesium sulphate versus placebo in the management of women with severe pre-eclampsia.
To determine whether the administration of prophylactic intravenous magnesium sulphate reduces the occurrence of eclampsia in women with severe pre-eclampsia.
                Randomised controlled trial.
                A tertiary referral obstetric unit.
                Eight hundred and twenty-two women with severe pre-eclampsia requiring termination of pregnancy by induction of labour or caesarean section.
                The women were randomised to receive either placebo (saline) or magnesium sulphate intravenously. The investigators were blinded to the contents of the pre-mixed solutions.
                The occurrence of eclampsia in the two groups.
                The data of 699 women were evaluated. Fourteen were withdrawn after randomisation. The overall incidence of eclampsia was 1.8%. Of 345 women who received magnesium sulphate, one developed eclampsia (0.3%); in the placebo group, 11/340 women (3.2%) developed eclampsia (relative risk 0.09; 95% confidence interval 0.01-0.69; P = 0.003).
                The use of intravenous magnesium sulphate in the management of women with severe pre-eclampsia significantly reduced the development of eclampsia.