Magnesium sulfate in labor and risk of neonatal brain lesions and cerebral palsy in low birth weight infants. The Neonatal Brain Hemorrhage Study Analysis Group.

OBJECTIVES We tested the hypothesis that administration of magnesium sulfate in labor protects against the development of neonatal brain lesions and cerebral palsy (CP) in low birth weight infants. METHODS Magnesium exposure was ascertained in a population-based cohort of 1105 infants weighing 2000 g or less through review of medical records of maternal magnesium sulfate administration and, where available, elevated maternal serum magnesium levels. Neonatal germinal matrix/intraventricular hemorrhage and parenchymal brain lesions were ascertained by a prospective, timed ultrasound scanning protocol in the first week of life. CP was ascertained at 2 years of age by clinical examination in 80% of survivors and by interview and medical record review in another 6% and was classified as disabling or nondisabling. RESULTS No significant reduction in risk of nondisabling CP (adjusted odds ratio [OR], 1.00; 95% confidence interval [CI], 0.53 to 1.88) or disabling CP [DCP] (adjusted OR, 0.63; 95% CI, 0.32 to 1.24) CP with magnesium exposure was found in a logistic regression model that controlled for gestational age, fetal growth, gender, multiple birth status, mode of delivery, amnionitis, and hypertensive disorders. In a small subset of infants, those with onset of parenchymal lesions at 7 days of age or later (n = 29), magnesium exposure was associated with a significantly reduced risk of DCP (OR, 0.10; 95% CI, 0.02 to 0.65). Magnesium sulfate exposure was not associated with germinal matrix/intraventricular hemorrhage (adjusted OR, 0.89; 95% CI, 0.64 to 1.25) or with parenchymal brain lesions (adjusted OR, 0.83; 95% CI, 0.53 to 1.30). CONCLUSIONS The hypothesis that magnesium sulfate use reduces the risk of neonatal brain lesions or CP in low birth weight infants was not statistically supported in this study, although a modest reduction in risk of DCP cannot be excluded. The data further suggest that magnesium exposure may be associated with reduction in risk of CP in low birth weight infants who have late-onset brain lesions, but this unpredicted observation requires confirmation in another data set.