Magnesium Before an Early Birth: What the Latest Evidence Tells Families About Protecting a Premature Baby's Brain

A plain-language guide to the 2026 corrected Cochrane review by Shepherd and colleagues, which pooled six trials of magnesium sulphate given to mothers to lower the chance of cerebral palsy

Before a very early birth, mothers are often given a drip of a medicine called magnesium sulphate to help protect the baby's brain. A 2026 update of the leading review of six trials confirms that it lowers the chance of cerebral palsy at age two, from about 58 to about 41 in every 1,000 children, and serious complications for mothers were very rare. The update corrects one earlier claim: magnesium no longer clearly reduces severe bleeding in the baby's brain.

Why a baby's brain is vulnerable when birth comes early

Babies born many weeks early arrive with brains that are still developing quickly, and they face a higher chance of problems that can last a lifetime. One of the most important is cerebral palsy, a lifelong condition that affects movement and posture, so anything that lowers the chance of it happening matters to families. This article explains what the newest summary of the research says about one of the few treatments that can help.

How a medicine for high blood pressure in pregnancy became a brain-protection treatment

Magnesium sulphate is an old, inexpensive medicine given through a drip into a vein. For many years it was used mainly for pre-eclampsia, a dangerous rise in blood pressure during pregnancy. In the 1990s, researchers noticed something unexpected: babies whose mothers had received magnesium for pre-eclampsia seemed to have less brain injury and less cerebral palsy, as the authors of the new review describe [1]. In one study of 449 very small premature babies, bleeding in the brain affected 1 of the 40 babies whose mothers had pre-eclampsia, compared with 71 of the 409 others, or about 1 in 6 [2].

A pattern noticed in this way is only a clue, so researchers ran randomised trials. In a randomised trial, a fair process like a coin toss decides which mothers receive magnesium and which receive a dummy drip of salt water (a placebo), so the two groups can be compared fairly. Over the following years, trials took place in 16 hospitals across Australia and New Zealand [3], in 20 hospitals of a large United States research network [4] and in 18 French hospitals [5]. Each trial on its own was too small to give a clear answer. In 2009, a Cochrane review, which is a careful summary that combines all the good-quality trials on one question, put the results together and concluded that magnesium did lower the chance of cerebral palsy [6]. After that, the World Health Organization included the treatment in its 2015 recommendations for improving outcomes after preterm birth [7][1], and hospitals in many countries made it routine. Questions remained, though: did the benefit last into school years, did it help babies born a little later, and how much did mothers notice side effects?

What the reviewers did this time

The new review, led by Emily Shepherd and published in September 2026, is a corrected version of a 2024 update [8]. It brings together six randomised trials involving 5,917 pregnant women and 6,759 babies. The trials were carried out in the United States, Australia and New Zealand, Denmark and France. Two of them were newer: one in 14 Danish hospitals [9] and one in 24 hospitals in Australia and New Zealand that focused on women 30 to 34 weeks pregnant [10]. Every trial compared magnesium sulphate with a salt-water placebo in women likely to give birth before 34 weeks. The reviewers also checked carefully that each study was trustworthy, and they rated how sure we can be about each result, from "high certainty" (very unlikely to change with more research) down to "very low certainty" [1].

What the review found for babies

The main finding is reassuringly clear and rated high certainty. By two years of age, cerebral palsy affected about 58 in every 1,000 children whose mothers had the placebo, compared with about 41 in every 1,000 whose mothers had magnesium. Put another way, for roughly every 60 babies whose mothers receive magnesium before birth, one child is spared cerebral palsy. The chance of a baby either dying or having cerebral palsy also went down, from about 138 to about 120 in every 1,000. Magnesium did not clearly change the chance of a baby dying on its own, which means the benefit is not explained by fewer babies surviving [1].

The one finding that changed

The 2024 version of the review said magnesium probably also reduced severe bleeding inside the baby's brain, known as severe intraventricular haemorrhage [8]. After the trial teams sent the reviewers more information about this outcome, the reviewers recalculated it. With the new data, about 41 in every 1,000 babies in the placebo groups and about 33 in every 1,000 in the magnesium groups would be expected to have severe bleeding, a difference small enough that it could be due to chance. The reviewers now say magnesium probably makes little or no difference to severe brain bleeding [1]. The review does not say which trial's data changed the result. This is a good example of science correcting itself in the open, and it does not change the main conclusion about cerebral palsy.

What it means for mothers

Magnesium can be uncomfortable. Many women feel warm and flushed, notice discomfort in the arm where the drip goes in, or feel sick, sweaty or dizzy. Side effects strong enough to stop the drip happened in about 61 in every 1,000 women given magnesium, compared with about 19 in every 1,000 given the placebo. Serious complications, such as breathing or heart problems, were very rare: across four trials of 5,300 women, the only serious event recorded was one death of a mother in a placebo group. Magnesium probably made little or no difference to the chance of a caesarean birth or of heavy bleeding after birth [1]. An earlier review of magnesium given for any reason in pregnancy also found it was not linked to more life-threatening problems, while stressing that staff should monitor women carefully [11].

What we still don't know

Only two of the trials followed children until they were at school, and many children could not be traced. At school age, the review found little or no difference in cerebral palsy between the groups, but the reviewers rate this evidence as low certainty, so it is too uncertain to say whether the benefit lasts or fades [1]. The Australian and New Zealand follow-up of children aged 6 to 11 years [12] and the French follow-up [13] found no signs of harm. One trial found possibly more two-year-olds with behaviour scores in a range that might need attention, but the reviewers caution this may be a chance finding [1].

There are other limits worth knowing. The search for trials ended in March 2023, so newer studies are not included. All six trials took place in wealthy countries, while cerebral palsy linked to pregnancy and birth is more common in some lower-income regions [14]. Cerebral palsy in the trials was diagnosed by age two using older methods; today, specialists can often recognise it much earlier using careful observation of a baby's movements [15], as described in our article on early detection of cerebral palsy. Seven of the nine review authors had worked on trials included in the review, so the two who had not handled the data checking for those trials.

A separate 2024 analysis that In[Neo]Sight covered in an earlier article counted seven trials rather than six and reached almost the same answer on cerebral palsy [16]. The difference seems to be that the extra trial gave magnesium to treat pre-eclampsia rather than to protect the baby's brain; we believe, from its description, that it is the Magpie trial, a study in many countries whose follow-up of children covered 125 centres in 19 countries, which the Cochrane reviewers left out for that reason, and whose children showed no clear difference at 18 months [17].

Questions families might ask

If you are expecting to give birth early, it is reasonable to ask your care team whether magnesium is recommended for you, how long the drip will run, and what side effects to tell the nurses about. If your baby has already been born, knowing that magnesium was given can be reassuring, but it is one part of a larger picture of care, and it does not mean your child will or will not have any particular outcome. Your baby's doctors can explain how they will watch your child's development.

What researchers are working on next

The reviewers want studies that follow children into their teenage and adult years, research on which mothers benefit most and which dose works best, and trials in low- and middle-income countries. They also call for a fresh combined analysis of each child's data from all the trials, including the two newer ones [1].

Conclusion

For families facing an early birth, the message from the 2026 review is steady and hopeful. Giving magnesium sulphate to the mother shortly before a very early birth lowers the chance that her child will have cerebral palsy at age two, with side effects that are often unpleasant but rarely serious. It should no longer be described as preventing severe brain bleeding, and researchers are still working out whether its protection lasts into the school years.

References

  1. Shepherd ES, Goldsmith S, Doyle LW, et al. Magnesium sulphate for women at risk of preterm birth for neuroprotection of the fetus. Cochrane Database Syst Rev. 2026;9(9):CD004661. doi:10.1002/14651858.CD004661.pub5 ↩
  2. Kuban KC, Leviton A, Pagano M, Fenton T, Strassfeld R, Wolff M. Maternal toxemia is associated with reduced incidence of germinal matrix hemorrhage in premature babies. J Child Neurol. 1992;7(1):70-76. doi:10.1177/088307389200700113 ↩
  3. Crowther CA, Hiller JE, Doyle LW, Haslam RR. Effect of magnesium sulfate given for neuroprotection before preterm birth: a randomized controlled trial. JAMA. 2003;290(20):2669-2676. doi:10.1001/jama.290.20.2669 ↩
  4. Rouse DJ, Hirtz DG, Thom E, et al. A randomized, controlled trial of magnesium sulfate for the prevention of cerebral palsy. N Engl J Med. 2008;359(9):895-905. doi:10.1056/NEJMoa0801187 ↩
  5. Marret S, Marpeau L, Zupan-Simunek V, et al. Magnesium sulphate given before very-preterm birth to protect infant brain: the randomised controlled PREMAG trial. BJOG.* 2007;114(3):310-318. doi:10.1111/j.1471-0528.2006.01162.x ↩
  6. Doyle LW, Crowther CA, Middleton P, Marret S, Rouse D. Magnesium sulphate for women at risk of preterm birth for neuroprotection of the fetus. Cochrane Database Syst Rev. 2009:CD004661. doi:10.1002/14651858.CD004661.pub3 ↩
  7. World Health Organization. WHO recommendations on interventions to improve preterm birth outcomes. Geneva: World Health Organization; 2015. ISBN 978 92 4 150898 8. https://www.who.int/publications/i/item/9789241508988 ↩
  8. Shepherd ES, Goldsmith S, Doyle LW, et al. Magnesium sulphate for women at risk of preterm birth for neuroprotection of the fetus. Cochrane Database Syst Rev. 2024;5(5):CD004661. doi:10.1002/14651858.CD004661.pub4 ↩
  9. Wolf HT, Brok J, Henriksen TB, et al. Antenatal magnesium sulphate for the prevention of cerebral palsy in infants born preterm: a double-blind, randomised, placebo-controlled, multi-centre trial. BJOG. 2020;127(10):1217-1225. doi:10.1111/1471-0528.16239 ↩
  10. Crowther CA, Ashwood P, Middleton PF, McPhee A, Tran T, Harding JE. Prenatal Intravenous Magnesium at 30-34 Weeks' Gestation and Neurodevelopmental Outcomes in Offspring: The MAGENTA Randomized Clinical Trial. JAMA. 2023;330(7):603-614. doi:10.1001/jama.2023.12357 ↩
  11. Bain ES, Middleton PF, Crowther CA. Maternal adverse effects of different antenatal magnesium sulphate regimens for improving maternal and infant outcomes: a systematic review. BMC Pregnancy Childbirth. 2013;13:195. doi:10.1186/1471-2393-13-195 ↩
  12. Doyle LW, Anderson PJ, Haslam R, Lee KJ, Crowther C. School-age outcomes of very preterm infants after antenatal treatment with magnesium sulfate vs placebo. JAMA. 2014;312(11):1105-1113. doi:10.1001/jama.2014.11189 ↩
  13. Chollat C, Enser M, Houivet E, et al. School-age outcomes following a randomized controlled trial of magnesium sulfate for neuroprotection of preterm infants. J Pediatr. 2014;165(2):398-400.e3. doi:10.1016/j.jpeds.2014.04.007 ↩
  14. McIntyre S, Goldsmith S, Webb A, et al. Global prevalence of cerebral palsy: A systematic analysis. Dev Med Child Neurol. 2022;64(12):1494-1506. doi:10.1111/dmcn.15346 ↩
  15. Novak I, Morgan C, Adde L, et al. Early, Accurate Diagnosis and Early Intervention in Cerebral Palsy: Advances in Diagnosis and Treatment. JAMA Pediatr. 2017;171(9):897-907. doi:10.1001/jamapediatrics.2017.1689 ↩
  16. Jafarabady K, Shafiee A, Eshraghi N, et al. Magnesium sulfate for fetal neuroprotection in preterm pregnancy: a meta-analysis of randomized controlled trials. BMC Pregnancy Childbirth. 2024;24(1):519. doi:10.1186/s12884-024-06703-9 ↩
  17. Magpie Trial Follow-Up Study Collaborative Group. The Magpie Trial: a randomised trial comparing magnesium sulphate with placebo for pre-eclampsia. Outcome for children at 18 months. BJOG. 2007;114(3):289-299. doi:10.1111/j.1471-0528.2006.01165.x ↩