Key messages
Magnesium sulphate given to women at risk of preterm birth for protecting their babies' brains reduces cerebral palsy, and the combined outcome of death or cerebral palsy, in their children up to two years of age, when compared with placebo.
Future research in this area should focus on the effects of treatment:
• on children when they are adolescents and adults; and
• for different groups of women at risk of preterm birth, and with different ways of giving magnesium sulphate.
What is magnesium sulphate?
Magnesium sulphate is a common medicine used across the world for different complications in pregnancy.
Why is this important for women at risk of preterm birth and their babies?
Babies born early (preterm, before 37 weeks of pregnancy) have a higher risk of complications including death and disabilities, such as cerebral palsy. In recent years, magnesium sulphate has been given to women who are likely to have their babies preterm (because of spontaneous preterm labour, or a medical indication to plan an induction of labour or caesarean birth early) to help protect their babies' brains and prevent these complications.
What did we want to find out?
We wanted to find out if magnesium sulphate is better than placebo (a 'dummy' treatment that does not contain any medicine but appears identical to the medicine being tested) at protecting the brains of babies likely to be born preterm.
We were interested in the effect of magnesium sulphate on important outcomes, including: death (of the babies, or later as children), cerebral palsy, and major 'neurodevelopmental disability' (which might include serious outcomes like cerebral palsy, blindness, deafness, or global cognitive or intellectual impairment). We were also interested in the effect on important outcomes for women, including serious complications of magnesium sulphate (death, respiratory or cardiac arrest), and stopping treatment because of side effects.
What did we do?
We searched for studies that looked at whether magnesium sulphate caused benefits or harms for women and their preterm babies when compared to placebo or no treatment. We compared and summarised results and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found six studies involving 5917 women at less than 34 weeks of pregnancy and their 6759 babies. The studies were all conducted in high-income countries. The included studies compared magnesium sulphate with placebo.
Main results
Compared with placebo, magnesium sulphate in women at risk of having their babies preterm:
• reduces cerebral palsy (evidence from 6 studies with 6107 children) and the combined outcome of death or cerebral palsy (6 studies, 6481 children) for children up to two years of age;
• probably makes little to no difference in death (6 studies, 6759 children), major neurodevelopmental disability (1 study, 987 children), or the combined outcome of death or major neurodevelopmental disability (3 studies, 4279 children), for children up to two years of age;
• may make little to no difference in the above-mentioned outcomes for children at early school age;
• may make little to no difference in serious complications of treatment for women (4 studies, 5300 women), but probably increases women stopping treatment because of side effects (3 studies, 4736 women).
What are the limitations of the evidence?
We are confident in our finding that magnesium sulphate reduces cerebral palsy, and the combined outcome of death or cerebral palsy, in children up to two years of age.
We have little confidence in the evidence for outcomes of children at school age, as studies could not provide data for all children, and there are not yet enough studies/data to be certain about the results.
We have little confidence in our finding that magnesium sulphate makes little to no difference in serious complications of treatment for women, as there was only one complication reported in one study. We have moderate confidence in our findings that magnesium sulphate probably increases women stopping treatment because of side effects, as the findings differed across studies, probably because of different decision-making processes for stopping treatment.
The results of further research for the outcomes in which we have limited confidence could differ from the results of this review.
How up-to-date is this evidence?
The evidence is current to 17 March 2023.