Should magnesium sulfate be used for fetal neuroprotection?

Preterm birth is a major risk factor for CP; infants born at less than 34 completed weeks' gestation constitute about 25% of all new cases. Magnesium sulfate is known to reduce spontaneous and induced myometrial contractions and has been used widely in obstetrics as a tocolytic agent.^1,2 However, its value in that setting has been questioned because it has not been shown to reduce the frequency of delivery within 48 hours compared with placebo or no therapy (relative risk [RR], 0.75; 95% confidence interval [CI], 0.54-1.03).^3,4 Recently, however, investigators hypothesized that magnesium sulfate could provide neuroprotection through reduced vascular instability and hypoxia-reperfusion injury and/or reductions in cytokine- or excitatory amino acid-induced damage. This has led investigators to evaluate its potential in preventing CP.

Clinical basis for recommending magnesium sulfate as a neuroprotectant

Given this evidence, magnesium sulfate treatment before an anticipated early preterm birth may be protective against CP. However, one must be cautious, because the benefits of antenatal treatment were identified only in secondary analyses. It should also be noted that no life-threatening events or maternal deaths were reported in any of the more than 3,000 women who received the drug in the randomized trials.¹³

Based on these recent findings, ACOG recognized that none of the individual studies found a benefit with respect to the primary outcome and that although the cumulative evidence suggests a neuroprotective effect, no firm recommendation was issued for or against therapy. The decision was left to the individual physician who should, if he or she chooses to use magnesium for this purpose, "develop specific guidelines regarding inclusion criteria, treatment regimens, concurrent tocolysis, and monitoring in accordance with one of the larger trials."¹⁴