Neonatal outcomes after in-utero exposure to magnesium sulphate: a retrospective analysis

Background: Magnesium sulphate (MgSO4) is routinely administered to pregnant women as a tocolytic and as a neuroprotective agent against cerebral palsy and motor impairment in preterm neonates. However, concerns have recently been arising regarding its effects in the neonate, including cardiovascular, intestinal, and neurological adverse effects. Our goal is to analyse prenatal MgSO4 administration and neonatal outcomes. Methods: We conducted a retrospective study that included all neonates born under 32 weeks of gestational age admitted to our Neonatal Intensive Care Unit between January 2016 and December 2019. Patients with life-threatening congenital malformations were excluded. Gestational, perinatal and outcome data were collected and statistically analysed. Results: One hundred and eighteen infants were included, of which 61 (51.7%) had been exposed to MgSO4 in utero. Mothers treated with MgSO4 were more likely also to have received corticosteroids for lung maturation and/or perinatal antibiotics. All but 5 (95.8%) infants needed post-natal resuscitation manoeuvres. Neonates that were prenatally exposed to MgSO4 were less likely to require such manoeuvres (p = 0.039), and immediate oxygen therapy (p = 0.015) was less frequently required. The median neonatal serum magnesium was higher in those exposed to MgSO4 (2.51 mEq/L) than in non-exposed (1.87 mEq/L) (p < 0.001). Neonatal serum magnesium values had a positive correlation with maternal prenatal values, with a Spearman's value of 0.78 (p < 0.001). Neonates prenatally exposed to MgSO4 were less likely to require surfactant treatment or aminergic support as well as less likely to have a persistent ductus arteriosus. No other statistically significant differences were found when comparing both groups for other outcomes. Conclusion: Prenatal exposure to MgSO4 is apparently safe for preterm infants. However, the conduction of a larger, prospective study must confirm these data.