Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. There are many Cochrane Pregnancy and Childbirth reviews of interventions to prevent health problems in babies that are born early. One of these was updated in April 2024, looking at the evidence on the effects of receiving magnesium sulphate prior to early birth. Lead author, Emily Shepherd from the South Australian Health and Medical Research Institute and University of Adelaide in Australia tells us about the latest findings in this podcast, with a focus on the prevention of cerebral palsy.

Emily: Cerebral palsy is the most common physical disability in childhood. The chance of having cerebral palsy is higher for children born in low- or middle-income countries and for children born preterm. However, because there is no cure for cerebral palsy, prevention is crucial.
In the 1990s, observational studies began showing that magnesium sulphate might help protect babies' brains if they were going to be born preterm. In 2009, the previous version of our Cochrane review confirmed for the first time that, when given to pregnant patients at risk of preterm birth, it could provide neuroprotection for preterm fetuses.
As a result, over the last decade, magnesium sulphate has been introduced into clinical practice for this purpose across the world. However, there are still uncertainties about its use - including who to give it to, and how best to give it. So, in recent years, new trials and longer-term follow up of previous trials have been conducted.
Against this backdrop, we set out to re-evaluate whether magnesium sulphate given to pregnant individuals prior to preterm birth reduces the risk of cerebral palsy for children, and found that the evidence continues to support its use.
We identified six randomised trials, involving almost 6000 pregnant patients who were less than 34 weeks through their pregnancies, and their almost 6800 babies. The studies were all from high-income countries and compared magnesium sulphate given intravenously versus a placebo (or ‘dummy' treatment).
We found that magnesium sulphate reduces cerebral palsy, and the combined outcome of death or cerebral palsy, for children in their first two years of life; and we are confident in these findings. Magnesium sulphate also probably reduces the risk of severe intraventricular haemorrhage – which is bleeding inside or around the ventricles of the brain – for these babies. This was a new finding in this update of the review, which was not observed in the 2009 version.
We found that magnesium sulphate may result in little to no difference in outcomes for children by the time they reach school age. However, we don't have a lot of confidence in these findings, because there were so few trials and data assessing children at these later ages.
We also found that magnesium sulphate may make little to no difference to serious complications for pregnant individuals – such as death, and cardiac or respiratory arrest. However, we found that, compared with placebo, it probably increases pregnant patients stopping treatment because of more minor side effects – like low blood pressure, warmth or flushing, and arm discomfort.
There are still some important knowledge gaps in this up-to-date evidence base. Further research is required to evaluate longer-term benefits and harms for children; to explore how magnesium sulphate's effectiveness varies by characteristics of pregnant patients and treatment regimens; and to investigate how generalisable these findings are to families in low- and middle-income countries.
In summary, our 2024 review shows that magnesium sulphate given to pregnant individuals for preterm fetal neuroprotection reduces cerebral palsy, and death or cerebral palsy, for their children up to two years of age.

Mike: If you would like to read this updated evidence, the full review is available at Cochrane Library dot com. If you go to the website and search 'magnesium and neuroprotection for preterm babies', you'll see a link to it.