Antenatal Neuroprotective Magnesium Sulfate in Very Preterm Infants and Its Association With Feeding Intolerance

Magnesium sulfate (MgSO 4 ) treatment is widely used for fetal neuroprotection despite the controversy concerning the side effects. There is limited data regarding the impact of various cumulative maternal doses and neonatal serum magnesium (Mg) levels on short-term neonatal morbidity and mortality. We opted to carry out a study to determine the impact of neonatal serum Mg levels on neonatal outcomes.

We conducted this prospective observational study between 2017 and 2021. Antenatal MgSO 4 was used for neuroprotective purpose only during the study period. Inborn preterm infants delivered between 23 and 31 6/7 weeks of gestation were enrolled consecutively. Babies who underwent advanced resuscitation in the delivery room, inotropic treatment due to hemodynamic instability in the first 7 days of life, >12 hours since the discontinuation of maternal MgSO 4 treatment, severe anemia, and major congenital/chromosomal anomalies were excluded from the study. The subgroup of babies with serum Mg level at the 6th hour of life underwent an analysis. A neonatal Mg concentration of 2.5 mg/dL was used to classify MgSO 4 -exposed patients into 2 groups (<2.5 mg/dL and ≥2.5 mg/dL). Another analysis was performed between babies whose mothers were exposed to MgSO 4 and those not exposed. Finally, the groups' neonatal outcomes were compared.

Of the 584 babies, 310 received antenatal MgSO 4 . The birth weights were significantly lower in the MgSO 4 exposed group (1113 ± 361 g vs 1202 ± 388 g, P = 0.005). Antenatal corticosteroid usage and intrauterine growth restriction were also noted to be higher. The MgSO 4 group was more likely to have bronchopulmonary dysplasia, prolonged invasive ventilation, necrotizing enterocolitis, delayed enteral nutrition, and feeding intolerance ( P < 0.05). MgSO 4 treatment was shown as an independent risk factor for feeding intolerance when corrected for confounders (odds ratio 2.13, 95% confidence interval: 1.4-3.1, P = 0.001). Furthermore, serum Mg level significantly correlated with feeding intolerance ( r = 0.21, P = 0.002).

This study highlighted the effect of MgSO 4 treatment and the potential superiority of serum Mg level as a predictor of immediate neonatal outcomes, particularly delayed enteral nutrition and feeding intolerance. Further studies are warranted to ascertain the optimal serum Mg concentration of preterm infants in early life to provide maximum benefit with minimal side effects.