Magnesium sulphate and other anticonvulsants for women with pre-eclampsia

Abstract

Pre-eclampsia is a relatively common complication of pregnancy. Eclampsia, the occurrence of one or more convulsions (fits) in association with the syndrome of pre-eclampsia, is a rare but serious complication. Anticonvulsants are used in the belief they help prevent eclamptic fits and so improve outcome. The objective was to assess the effects of anticonvulsants for pre-eclampsia on the women and their children. We searched the Cochrane Pregnancy and Childbirth Group trials register (28 November 2002), and the Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2002). Randomised trials comparing anticonvulsants with placebo or no anticonvulsants or comparisons of different anticonvulsants in women with pre-eclampsia. Two reviewers assessed trial quality and extracted data independently. Six trials (11,444 women) compared magnesium sulphate with placebo or no anticonvulsant. There was more than a halving in the risk of eclampsia associated with magnesium sulphate (relative risk (RR) 0.41, 95% confidence interval (CI) 0.29 to 0.58; number needed to treat (NNT) 100, 95% CI 50 to 100). The risk of dying was non-significantly reduced by 46% for women allocated magnesium sulphate (RR 0.54, 95% CI 0.26 to 1.10). For serious maternal morbidity RR 1.08, 95% CI 0.89 to 1.32. Side effects were more common with magnesium sulphate (24% versus 5%; RR 5.26, 95% CI 4.59 to 6.03; NNT for harm 6, 95% CI 6 to 5). The main side effect was flushing. Risk of placental abruption was reduced for women allocated magnesium sulphate (RR 0.64, 95% CI 0.50 to 0.83; NNT 100, 95% CI 50 to 1000). Women allocated magnesium sulphate had a small increase (5%) in the risk of caesarean section (95% CI 1% to 10%). There was no overall difference in the risk of stillbirth or neonatal death (RR 1.04, 95% CI 0.93 to 1.15). Magnesium sulphate was better than phenytoin for reducing the risk of eclampsia (two trials 2241 women; RR 0.05, 95% CI 0.00 to 0.84), but with an increased risk of caesarean section (RR 1.21, 95% CI 1.05 to 1.41). It was also better than nimodipine (1 trial, 1650 women; RR 0.33, 95% CI 0.14 to 0.77). Magnesium sulphate more than halves the risk of eclampsia, and probably reduces the risk of maternal death. It does not improve outcome for the baby, in the short term. A quarter of women have side effects, particularly flushing.