Clinical trials support the efficacy and safety of magnesium sulfate for cerebral palsy prevention. We evaluated the implementation of a clinical protocol for the use of magnesium for cerebral palsy prevention in our large women's hospital, focusing on uptake, indications, and safety. We performed a review of selected gravidas with threatened or planned delivery before 32 weeks of gestation from October 2007 to February 2011. The primary study outcome was the change in the rate of predelivery administration of magnesium sulfate over this time period. Three hundred seventy-three patients were included. In 2007, before guideline implementation, 20% of eligible gravidas (95% confidence interval [CI] 9.1-35.6%) received magnesium before delivery compared with 93.9% (95% CI 79.8-99.3%) in the final 2 months of the study period (P<.001). Dosing did not vary significantly over the 4 study years: the median number of treatments was one, the total predelivery median dose ranged from 15 to 48 g, and the median duration of therapy ranged from 3 to 12 hours. After 3 years, magnesium administration was almost universal among patients diagnosed with preeclampsia, preterm labor, or preterm premature rupture of membranes (95.4%), whereas patients delivered preterm for fetal growth restriction were significantly less likely to receive predelivery magnesium (44%, P<.001). No maternal or perinatal magnesium-attributable morbidity was noted. Among patients eligible for the protocol who received magnesium, 84.2% delivered before 32 weeks of gestation. It is feasible to implement a magnesium sulfate cerebral palsy prevention protocol into clinical practice. III.