Risk factors and prediction model for high neonatal serum magnesium concentrations in prenatal maternal magnesium sulfate therapy

Prenatal maternal magnesium sulfate therapy is commonly used in the obstetrics field. An association between high neonatal magnesium concentration and neonatal toxicity has been reported. The main purpose of this study is to analyse the risk factors for high neonatal serum magnesium concentrations (>4.5 mg/dL) in prenatal maternal magnesium therapy. This retrospective study employed the electronic medical record systems of seven tertiary care centres under the College of Medicine, the Catholic University of Korea, from January 2009 to March 2021. Among 34,995 mothers who gave birth within this period, mother-neonate pairs who received maternal magnesium sulfate therapy on the day of delivery were included. Cases only with neonate serum magnesium concentration measured within 24 hours of birth were included in the study. The number of fetuses greater than triplet and intrauterine fetal death was excluded. A total of 596 mother-neonate pairs were obtained. Neonates with serum magnesium concentration of 4.5 mg/dL or higher were 4.2% in 25 neonates (high group). Stepwise multivariate logistic regression analysis was performed, which resulted in the following factors being associated with high neonatal magnesium concentration: “gestational age at delivery”, “maternal serum magnesium concentrations”, “maternal glomerular filtration rate”, and “duration of magnesium sulfate treatment.” We constructed a model for predicting high neonatal serum magnesium concentrations using these four factors. The area under the receiver operating characteristic was 0.952. This model showed a sensitivity of 100%, a specificity of 86.0%, a positive predictive value of 23.8%, and a negative predictive value of 100%. We have identified four predictors and a model of high neonatal serum magnesium concentrations that can guide maternal magnesium treatment. Our study will allow safer use of magnesium and better prognosis for neonates.