Administered to pregnant women before preterm birth at 30–34 weeks’ gestation, the survival of children free of cerebral palsy at 2 years was not improved, the MAGENTA randomized controlled trial shows. The study was conducted in 24 Australian and New Zealand hospitals between 2012 and early 2018 and had limited power to detect small between-group differences, the authors note.
Based on a primary outcome of death (stillbirth, death of a live-born infant before hospital discharge, or death after hospital discharge before 2 years’ corrected age) or cerebral palsy (loss of motor function and abnormalities of muscle tone and power), the study showed the following: “Of the 1,433 pregnant individuals enrolled (mean age, 30.6 [SD, 6.6] years; 46 [3.2%] self-identified as Aboriginal or Torres Strait Islander, 237 [16.5%] as Asian, 82 [5.7%] as Māori, 61 [4.3%] as Pacific, and 966 [67.4%] as White) and their 1,679 infants, 1,365 (81%) offspring (691 in the magnesium group and 674 in the placebo group) were included in the primary outcome analysis. Death or cerebral palsy at 2 years’ corrected age was not significantly different between the magnesium and placebo groups (3.3% [23 of 691 children] vs 2.7% [18 of 674 children], respectively; risk difference, 0.61% [95% CI, −1.27% to 2.50%]; adjusted relative risk [RR], 1.19 [95% CI, 0.65 to 2.18]). Components of the primary outcome did not differ between groups. Neonates in the magnesium group were less likely to have respiratory distress syndrome vs the placebo group (34% [294 of 858] vs 41% [334 of 821], respectively; adjusted RR, 0.85 [95% CI, 0.76 to 0.95]) and chronic lung disease (5.6% [48 of 858] vs 8.2% [67 of 821]; adjusted RR, 0.69 [95% CI, 0.48 to 0.99]) during the birth hospitalization. No serious adverse events occurred; however, adverse events were more likely in pregnant individuals who received magnesium vs placebo (77% [531 of 690] vs 20% [136 of 667], respectively; adjusted RR, 3.76 [95% CI, 3.22 to 4.39]). Fewer pregnant individuals in the magnesium group had a cesarean delivery vs the placebo group (56% [406 of 729] vs 61% [427 of 704], respectively; adjusted RR, 0.91 [95% CI, 0.84 to 0.99]), although more in the magnesium group had a major postpartum hemorrhage (3.4% [25 of 729] vs 1.7% [12 of 704] in the placebo group; adjusted RR, 1.98 [95% CI, 1.01 to 3.91]).”
Editorial: “The time has come to limit intrapartum magnesium for neurological protection to patients who are at risk to give birth before 30 weeks’ gestation,” editorialists write. “In the current trial, there were no serious cardiovascular or respiratory outcomes that occurred in the pregnant individuals associated with the magnesium infusion. However, children exposed to magnesium were more likely to have high behavior scores, indicating increased behavioral problems. Concerns regarding other adverse outcomes associated with administration of prenatal magnesium have been reported over the past decade. Most of these concerns have focused on gastrointestinal complications in infants born before 25 weeks’ gestation, including an increased risk of meconium-related ileus, spontaneous intestinal perforation, and necrotizing enterocolitis.”