Four large, randomized placebo-controlled trials of antenatal MgSO4 for fetal neuroprotection have been conducted; separately and together, they demonstrate that MgSO4 diminishes the risk of cerebral palsy among the survivors of early preterm birth. A meta-analysis of three of these trials, and a fourth, smaller one, shows that not only does the maternal administration of magnesium sulfate for fetal neuroprotection lower the subsequent risk of childhood cerebral palsy but also the combined risk of cerebral palsy or death. Since the publication of that meta-analysis, an additional trial also found a lower rate of cerebral palsy with MgSO4. The use of magnesium sulfate to prevent cerebral palsy has become widespread. The Netherlands, Australia, New Zealand, the United Kingdom, and Canada have promulgated national guidelines for the use of magnesium sulfate to prevent cerebral palsy. All fields are reviewed in this chapter.