Association between the use of antenatal magnesium sulfate in preterm labor and adverse health outcomes in infants

OBJECTIVE: The purpose of this study was to determine whether the use of antenatal magnesium sulfate prevents adverse outcomes (neonatal intraventricular hemorrhage, periventricular leucomalacia, death, and cerebral palsy). STUDY DESIGN: In a controlled trial, we randomized mothers in preterm labor to magnesium sulfate, "other" tocolytic, or placebo. At delivery, umbilical cord blood was collected for the later determination of serum ionized magnesium levels. Neonatal cranial ultrasound scans were obtained periodically for the diagnosis of intraventricular hemorrhage and periventricular leucomalacia. Among survivors, the diagnosis of cerebral palsy was made at age 18 months. RESULTS: Children with adverse outcomes had higher umbilical cord magnesium levels at delivery. In regression models that controlled for confounders, which included very low birth weight, magnesium remained a significant risk factor (adjusted odds ratio, 3.7; 95% CI, 1.1-11.9; P=.03). CONCLUSION: Contrary to original hypotheses, this randomized trial found that the use of antenatal magnesium sulfate was associated with worse, not better, perinatal outcome in a dose-response fashion.