Very-Iow-birthweight neonates whose mothers were treated with magnesium sulfate for preterm labor or preeclampsia were found to have a reduced incidence of cerebral palsy at 3 years (Grether, 2000; Nelson, 1995). Because of this, randomized trials were designed to investigate this hypothesis. In one trial, 1063 women at risk of delivery before 30 weeks were given magnesium sulfate or placebo (Crowther, 2003). Magnesium exposure improved some perinatal outcomes. Namely, rates of both neonatal death and cerebral palsy were lower in the magnesium-treated group-but this study was not suiciently powered. The multicenter French trial reported by Marret and associates (2008) had similar problems.
More convincing evidence for magnesium neuroprotection came from the MFMU Network study-Beneicial Eects of Antenatal Magnesium Suote-BM-Study (Rouse, 2008). This was a placebo-controlled trial in 224e1 women at imminent risk for preterm birth between 24 and 31 weeks. Women randomized to magnesium sulfate were given a 6-g bolus over 20 to 30 minutes followed by a maintenance infusion of 2 g per hour. Magnesium sulfate was actually infusing at the time of delivery in approximately half of the treated women. A 2-year follow-up was available for 96 percent of the children. Results are shown in Table 42-10. his trial can be interpreted diferently depending on statistical methodologies employed. Some interpret these indings to mean that magnesium infusion prevents cerebral palsy regardless of the gestational age at which therapy is given. Those with a difering view conclude that this trial only supports use of magnesium sulfate for prevention of cerebral palsy before 28 weeks.
Subsequent to these studies, Doyle and associates (2009) reviewed five randomized trials to assess neuroprotective efects. A total of 6145 infants were studied, and these reviewers concluded that magnesium exposure compared with no exposure significantly lowered risks for cerebral palsy. Rates of other neonatal morbidity did not difer significantly. It was calculated that treatment given to 63 women would prevent one case of cerebral plsy.
Controversy surrounding magnesium eicacy for neuroprotection prompted a debate at the 20e11 annual meeting of the Society for Maternal-Fetal Medicine. Rouse (2011) spoke for the beneits of magnesium sulfate, whereas Sibai (2011) challenged that the reported benefits were false positive due to random statistical error in the metaanalysis by Doyle (2009). Another peculiarity is the apparent lack of dose-response for eicacy (McPherson, 2014). Because none of the individual studies found a benefit from magnesium sulfate for fetal neuroprotection, the American College of Obstetricians and Gynecologists (20e1e6a) concluded that those electing prophylaxis should develop specific guidelines. To guide such therapy, the American College of Obstetricians and Gynecologists (20e12)
TABLE 42-10. Magnesium Sulfate for the Prevention of Cerebral Palsya
Infants with 2-year follow-up
Moderate or severe cerebral palsy: aSelected results from the Beneficial Efects of Antenatal Magnesium Sulfate (BEAM) Study. bWeeks' gestation at randomization.
CI = confidence index. Data from Rouse, 2008.
issued a Patient Saey Checklist for use of magnesium sulfate for neuroprotection. For those with PPROM, prophylaxis may similarly be considered. At Parkland Hospital, we provide magnesium sulfate for neuroprotection with threatened preterm delivery from 24°/7 to 276/7 weeks.