Objective To determine whether the administration of prophylactic intravenous magnesium sulphate reduces the occurrence of eclempsia in women with severe pre-eclampsia.
Design Randomised controlled trial.
Setting A tertiary referral obstetric unit.
Population Eight hundred and twenty-two women with severe pre-eclampsia requiring termination of pregnancy by induction of labour or caesarean section.
Methods 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.
Main outcome measure The occurrence of eclampsia in the two groups.
Results 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 Fourteen were withdrawn after randomisation.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).
Conclusion The use of intravenous magnesium sulphate in the management of women with severe pre-eclampsia significantly reduced the development of eclampsia.