Association between maternal serum ionized magnesium levels at delivery and neonatal intraventricular hemorrhage. Mittendorf R, Dambrosia J, Dammann O, et al. J Pediatr (May 2002); 140:540-6.

Objectives: To determine whether magnesium sulfate (MgSO₄) exposure is associated with a reduced risk for neonatal intraventricular hemorrhage (IVH).

Study design: In a randomized, controlled trial, women in preterm labor were randomly assigned to receive MgSO₄, "other" tocolytic, or saline control. At delivery, we collected maternal antecubital and umbilical cord blood for determination of serum ionized magnesium levels. Neonatal IVH was diagnosed by cranial ultrasonogram.

Results: Among 144 infants, 24 were diagnosed with IVH. Using crude intention-to-treat analysis, we found that 18% (13/74) of survivors exposed after birth to MgSO₄ had IVH compared with 16% (11/70) of babies who were not exposed. Infants who had IVH were more likely to have been delivered by mothers with higher serum ionized magnesium (Mg) levels (0.75 vs 0.56 mmol/L) (P = .01). Using multivariable logistic regression, we confirmed that higher Mg levels are a significant predictor of neonatal IVH (adjusted odds ratio, 15.8; 95% CI, 1.4-175.0) even when adjusted for birth weight, gestational age, antenatal hemorrhage, and neonatal glucocorticoid exposure.

Conclusions: In mothers with preterm labor, our data indicate that antenatal MgSO₄ exposure may be associated with an increased risk for IVH among their newborns.