Umbilical cord serum ionized magnesium level and total pediatric mortality

Objective: To estimate whether higher magnesium levels in umbilical cord bl ood at delivery are associated with increased total pediatric (fetal + neon atal + postneonatal) mortality. Methods: During the Magnesium and Neurologic Endpoints Trial, in addition t o randomizing mothers having preterm labor into arms containing magnesium s ulfate, other tocolytic agents, or saline controls, we obtained biologic sp ecimens at delivery, including umbilical cord vel nous blood on which was d etermined the serum ionized magnesium level using the AVL 988-4 analyzer (G raz, Austria). Laboratory results were then matched with the pediatric mort alities. The study power was based on the anticipated reductions in neonata l intraventricular hemorrhage related to magnesium usage from 18.9% to 4.4% . For alpha = .05, 1 - beta (power) = 80%, two tailed, the total number of infants needed would be 140. Results: Of 149 mothers who gave permission for randomization, ionized magn esium levels were available for 82 children. Seven deaths occurred (one imm ediately before delivery, three as neonates, and three in the postneonatal period). The median level of ionized magnesium among the seven dead childre n was 0.76 mmol/L among the 75 survivors, the median level of ionized magne sium was 0.55 mmol/L (Mann-Whitney U test, P = .03). Using multivariable lo gistic regression analysis, the association remained statistically signific ant when controlling for possible confounding factors (adjusted odds ratio 7.7, 95% confidence interval 1.2, 47.6, P = .03). Conclusion: These findings of a dose response between serum ionized magnesi um and deaths in children increase our concern about the improper use of to colytic magnesium. (C) 2001 by the American College of Obstetricians and Gy necologists.