In the 3 large, well-done randomized placebo-controlled trials, antenatal magnesium sulfate (MgSO ₄ ) reduced the risk of cerebral palsy among children who survived early preterm birth. Crowther and colleagues studied 1062 women. Moderate or severe cerebral palsy (inability to walk unaided) was significantly less frequent among children in the MgSO ₄ group, 3.4% vs 6.6%. In the National Institutes of Health Maternal-Fetal Medicine Units Network trial (the BEAM trial) 2241 women were enrolled. As in the trial of Crowther et al, MgSO ₄ significantly reduced the risk of moderate to severe cerebral palsy, 1.9% vs 3.5%. Among the offspring of women randomized <28 weeks, the respective risks were 2.7% and 6.1%. Marret et al studied 573 mothers: MgSO ₄ lowered the risk of cerebral palsy, 7.0% vs 10.2%. These 3 trials and 2 more (6145 children) are included in a Cochrane Systematic Review that concluded that MgSO ₄ reduced the risk of cerebral palsy by 32% but had no effect on fetal or infant mortality.

Should we wait for more data or an even more definitive trial? The BEAM trial cost $25 million and took 10 years to complete. It is doubtful that a comparable trial will ever be mounted. Thus for the foreseeable future (and perhaps forever), the debate will center on the data from the completed trials. Basic research may elucidate mechanisms, and individual level patient metaanalysis may help to more precisely quantify the benefits to various candidate subgroups, but the necessary clinical research has been done. Importantly, the confidence that we can place in the consistent results of the randomized trials is heightened , not diminished, by their different inclusion and exclusion criteria, and their administration of MgSO ₄ according to different protocols.

MgSO ₄ is inexpensive and its safety profile is excellent: there were no life-threatening events or deaths in any of the >3000 women in the Cochrane Review who received the drug. In the United States, 2% of women deliver <32 weeks’ gestation. If these women received MgSO ₄ prior to delivery, >1000 cases of handicapping cerebral palsy would be prevented safely and inexpensively every year in this country alone. To forgo this opportunity is irrationally nihilistic–it is time to use MgSO ₄ for fetal neuroprotection.