Prenatal Magnesium Sulfate and Functional Connectivity in Offspring at Term-Equivalent Age

Importance Understanding the effect of antenatal magnesium sulfate (MgSO 4 ) treatment on functional connectivity will help elucidate the mechanism by which it reduces the risk of cerebral palsy and death. Objective To determine whether MgSO 4 administered to women at risk of imminent preterm birth at a gestational age between 30 and 34 weeks is associated with increased functional connectivity and measures of functional segregation and integration in infants at term-equivalent age, possibly reflecting a protective mechanism of MgSO 4 . Design, Setting, and Participants This cohort study was nested within a randomized placebo-controlled trial performed across 24 tertiary maternity hospitals. Participants included infants born to women at risk of imminent preterm birth at a gestational age between 30 and 34 weeks who participated in the MAGENTA (Magnesium Sulphate at 30 to 34 Weeks’ Gestational Age) trial and underwent magnetic resonance imaging (MRI) at term-equivalent age. Ineligibility criteria included illness precluding MRI, congenital or genetic disorders likely to affect brain structure, and living more than 1 hour from the MRI center. One hundred and fourteen of 159 eligible infants were excluded due to incomplete or motion-corrupted MRI. Recruitment occurred between October 22, 2014, and October 25, 2017. Participants were followed up to 2 years of age. Analysis was performed from February 1, 2021, to February 27, 2024. Observers were blind to patient groupings during data collection and processing. Exposures Women received 4 g of MgSO 4 or isotonic sodium chloride solution given intravenously over 30 minutes. Main Outcomes and Measures Prior to data collection, it was hypothesized that infants who were exposed to MgSO 4 would show enhanced functional connectivity compared with infants who were not exposed. Results A total of 45 infants were included in the analysis: 24 receiving MgSO 4 treatment and 21 receiving placebo; 23 (51.1%) were female and 22 (48.9%) were male; and the median gestational age at scan was 40.0 (IQR, 39.1-41.1) weeks. Treatment with MgSO 4 was associated with greater voxelwise functional connectivity in the temporal and occipital lobes and deep gray matter structures and with significantly greater clustering coefficients (Hedge g , 0.47 95% CI, −0.13 to 1.07), transitivity (Hedge g , 0.51 95% CI, −0.10 to 1.11), local efficiency (Hedge g , 0.40 95% CI, −0.20 to 0.99), and global efficiency (Hedge g , 0.31 95% CI, −0.29 to 0.90), representing enhanced functional segregation and integration. Conclusions and Relevance In this cohort study, infants exposed to MgSO 4 had greater voxelwise functional connectivity and functional segregation, consistent with increased brain maturation. Enhanced functional connectivity is a possible mechanism by which MgSO 4 protects against cerebral palsy and death.