Magnesium sulphate leads to fewer maternal deaths and fewer further seizures than diazepam (Valium) when given for eclamptic seizures (fits).
Between two and eight in every 100 pregnant women develop pre-eclampsia (toxaemia), which usually means they have high blood pressure and protein in the urine. A small number of women with pre-eclampsia will also have a seizure (fit); this is called eclampsia. Eclampsia can occur in the second half of pregnancy, during labour, or after the birth. Women with eclampsia are given an anticonvulsant drug to control the eclamptic fit, and to prevent further fits. Eclampsia is an important condition because once women have an eclamptic fit they have a high risk of being seriously ill and dying. Worldwide, an estimated 358,000 women died in 2008 due to complications of pregnancy and childbirth, and 99% of these deaths are women in low- and middle-income countries. Overall, 15% of maternal deaths are associated with eclampsia. Eclampsia is more common in low- and middle-income countries than in high-income countries.
Our review of seven randomised trials, involving 1396 women, found that intravenous or intramuscular magnesium sulphate was substantially better than intravenous diazepam in reducing the risk of maternal death and of having further seizures. Treatment was for 24 hours unless there was an indication to continue for longer. Diazepam infusion was titrated against the level of sedation, with the aim of keeping the woman drowsy but rousable. Use of magnesium sulphate requires monitoring of respiration rate, tendon reflexes and urine output to avoid adverse effects.
Fewer babies had low Apgar scores at birth with magnesium sulphate than with diazepam and, although admissions to a special care nursery were similar, fewer babies in the magnesium sulphate group had a length of stay of more than seven days.
In other Cochrane reviews, magnesium sulphate was also substantially better than other drugs (phenytoin and lytic cocktail).