Treatment with magnesium prior to preterm birth at 30–34 weeks' is not neuroprotective

Reference

Crowther CA, Ashwood P, Middleton PF, McPhee A, Tran T, Harding JE, for the MAGENTA Study Group. Prenatal intravenous magnesium at 30-34 weeks’ gestation and neurodevelopmental outcomes in offspring: the MAGENTA randomized clinical trial. JAMA 2023;330(7):603-614. 

Synopsis

It is established that intravenous magnesium sulfate given to pregnant individuals prior to preterm birth at less than 30 weeks' gestation improved neurodevelopmental outcomes in offspring. This multicenter randomized controlled trial was conducted to assess its value when given to prior to preterm birth at 30 to 34 weeks'. Consenting pregnant individuals (N = 1433) were enrolled if birth was planned or definitely expected in the following 24 hours, and if they had no contraindication to magnesium sulfate infusion. The need for magnesium sulfate to treat preeclampsia was an exclusion criterion. Magnesium sulfate (4 g) or placebo was administered over 30 minutes. Surviving children (N = 1679) underwent neurodevelopmental assessment by a pediatrician and a trained outcomes assessor as closely as possible to 2 years' corrected age. The primary outcome of death or a cerebral palsy diagnosis at the 2-year assessment was not different between groups (1.6% vs 1.7%; NS). Secondary outcomes also did not differ for death, any neurological disability, any neurosensory impairments, or the severity of neurosensory impairments. Children with exposure to magnesium were more likely to have overall behavioral scores within the clinical problem range (40/389 [10%] vs 24/379 [6%]; adjusted relative risk 1.66; 95% CI 1.03 - 2.68; P = .04). This latter finding is of borderline statistical significance and the authors stated that they did not adjust for multiple comparisons. Note that the study was underpowered based on the calculations provided in the article. In addition, only approximately 80% of children were included in the analysis for the primary outcome.